<PAGE>

Exhibit 24

                                POWER OF ATTORNEY

WHEREAS, Kendle International Inc., an Ohio corporation (the "Company"),
proposes to file with the Securities and Exchange Commission under the
provisions of the Securities Exchange Act of 1934, as amended, and the Rules and
Regulations thereunder, an Annual Report on Form 10-K for the year ended
December 31, 2004; and

      WHEREAS, the undersigned is a director of the Company;

      NOW, THEREFORE, the undersigned hereby constitutes and appoints Karl
Brenkert III and Douglas W. Campbell, acting individually, his attorney, for him
and in his name, place and stead, and in such appointee's office and capacity in
the Company, to execute and file such Annual Report on Form 10-K, and thereafter
to execute and file any amendments or supplements thereto, hereby giving and
granting to said attorney full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises as fully to all intents and purposes as he might or could do if
personally present at the doing thereof, hereby ratifying and confirming all
that said attorney may or shall lawfully do or cause to be done by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has hereunto set his hand this ______
day of February, 2005.

                                                   /s/ Robert R. Buck
                                                   -------------------
                                                        (sign name)

                                                       Robert R. Buck
                                                       --------------
                                                        (print name)

<PAGE>

Exhibit 24

                                POWER OF ATTORNEY

WHEREAS, Kendle International Inc., an Ohio corporation (the "Company"),
proposes to file with the Securities and Exchange Commission under the
provisions of the Securities Exchange Act of 1934, as amended, and the Rules and
Regulations thereunder, an Annual Report on Form 10-K for the year ended
December 31, 2004; and

      WHEREAS, the undersigned is a director of the Company;

      NOW, THEREFORE, the undersigned hereby constitutes and appoints Karl
Brenkert III and Douglas W. Campbell, acting individually, his attorney, for him
and in his name, place and stead, and in such appointee's office and capacity in
the Company, to execute and file such Annual Report on Form 10-K, and thereafter
to execute and file any amendments or supplements thereto, hereby giving and
granting to said attorney full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises as fully to all intents and purposes as he might or could do if
personally present at the doing thereof, hereby ratifying and confirming all
that said attorney may or shall lawfully do or cause to be done by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has hereunto set his hand this 27th
day of February, 2005.

                                                   /s/ G. Steven Geis
                                                   ------------------
                                                       (sign name)

                                                       G.Steven Geis
                                                       -------------
                                                       (print name)

<PAGE>

Exhibit 24

                                POWER OF ATTORNEY

WHEREAS, Kendle International Inc., an Ohio corporation (the "Company"),
proposes to file with the Securities and Exchange Commission under the
provisions of the Securities Exchange Act of 1934, as amended, and the Rules and
Regulations thereunder, an Annual Report on Form 10-K for the year ended
December 31, 2004; and

      WHEREAS, the undersigned is a director of the Company;

      NOW, THEREFORE, the undersigned hereby constitutes and appoints Karl
Brenkert III and Douglas W. Campbell, acting individually, his attorney, for him
and in his name, place and stead, and in such appointee's office and capacity in
the Company, to execute and file such Annual Report on Form 10-K, and thereafter
to execute and file any amendments or supplements thereto, hereby giving and
granting to said attorney full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises as fully to all intents and purposes as he might or could do if
personally present at the doing thereof, hereby ratifying and confirming all
that said attorney may or shall lawfully do or cause to be done by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has hereunto set his hand this 25th
day of February, 2005.

                                                   /s/ Timothy E. Johnson
                                                   ----------------------
                                                       (sign name)

                                                      Timothy E. Johnson
                                                      ------------------
                                                        (print name)

<PAGE>

Exhibit 24

                                POWER OF ATTORNEY

WHEREAS, Kendle International Inc., an Ohio corporation (the "Company"),
proposes to file with the Securities and Exchange Commission under the
provisions of the Securities Exchange Act of 1934, as amended, and the Rules and
Regulations thereunder, an Annual Report on Form 10-K for the year ended
December 31, 2004; and

      WHEREAS, the undersigned is a director of the Company;

      NOW, THEREFORE, the undersigned hereby constitutes and appoints Karl
Brenkert III and Douglas W. Campbell, acting individually, his attorney, for him
and in his name, place and stead, and in such appointee's office and capacity in
the Company, to execute and file such Annual Report on Form 10-K, and thereafter
to execute and file any amendments or supplements thereto, hereby giving and
granting to said attorney full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises as fully to all intents and purposes as he might or could do if
personally present at the doing thereof, hereby ratifying and confirming all
that said attorney may or shall lawfully do or cause to be done by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has hereunto set his hand this 25th
day of February, 2005.

                                                   /s/ Donald C. Harrison
                                                   -----------------------
                                                       (sign name)

                                                      Donald C. Harrison
                                                      ------------------
                                                         (print name)

<PAGE>

Exhibit 24

                                POWER OF ATTORNEY

WHEREAS, Kendle International Inc., an Ohio corporation (the "Company"),
proposes to file with the Securities and Exchange Commission under the
provisions of the Securities Exchange Act of 1934, as amended, and the Rules and
Regulations thereunder, an Annual Report on Form 10-K for the year ended
December 31, 2004; and

      WHEREAS, the undersigned is a director of the Company;

      NOW, THEREFORE, the undersigned hereby constitutes and appoints Karl
Brenkert III and Douglas W. Campbell, acting individually, his attorney, for him
and in his name, place and stead, and in such appointee's office and capacity in
the Company, to execute and file such Annual Report on Form 10-K, and thereafter
to execute and file any amendments or supplements thereto, hereby giving and
granting to said attorney full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises as fully to all intents and purposes as he might or could do if
personally present at the doing thereof, hereby ratifying and confirming all
that said attorney may or shall lawfully do or cause to be done by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has hereunto set his hand this 28th
day of February, 2005.

                                                   /s/ Frederick A. Russ
                                                   ---------------------
                                                       (sign name)

                                                      Frederick A. Russ
                                                      -----------------
                                                        (print name)

<PAGE>

Exhibit 24

                                POWER OF ATTORNEY

WHEREAS, Kendle International Inc., an Ohio corporation (the "Company"),
proposes to file with the Securities and Exchange Commission under the
provisions of the Securities Exchange Act of 1934, as amended, and the Rules and
Regulations thereunder, an Annual Report on Form 10-K for the year ended
December 31, 2004; and

      WHEREAS, the undersigned is a director of the Company;

      NOW, THEREFORE, the undersigned hereby constitutes and appoints Karl
Brenkert III and Douglas W. Campbell, acting individually, his attorney, for him
and in his name, place and stead, and in such appointee's office and capacity in
the Company, to execute and file such Annual Report on Form 10-K, and thereafter
to execute and file any amendments or supplements thereto, hereby giving and
granting to said attorney full power and authority to do and perform each and
every act and thing whatsoever requisite and necessary to be done in and about
the premises as fully to all intents and purposes as he might or could do if
personally present at the doing thereof, hereby ratifying and confirming all
that said attorney may or shall lawfully do or cause to be done by virtue
hereof.

      IN WITNESS WHEREOF, the undersigned has hereunto set his hand this 26th
day of February, 2005.

                                                   /s/ Robert C. Simpson
                                                   ---------------------
                                                       (sign name)

                                                      Robert C. Simpson
                                                      -----------------
                                                       (print name)