An immunoconjugate having the formula - -, wherein: is an antibody or antigen binding fragment; is a linker; and is a maytansinoid or a maytansinoid analog, wherein said linker links to, wherein is selected from the group consisting of: i) a humanized antibody or antigen binding fragment thereof that specifically binds a human folate receptor 1, wherein the antibody or antigen binding fragment thereof comprises: (a) a heavy chain CDR1 comprising GYFMN (SEQ ID NO: 1); a heavy chain CDR2 comprising RIHPYDGDTFYNQKFQG (SEQ ID NO: 2); and a heavy chain CDR3 comprising YDGSRAMDY (SEQ ID NO: 3); and (b) a light chain CDR1 comprising KASQSVSF AGTSLMH (SEQ ID NO: 7); a light chain CDR2 comprising RASNLEA (SEQ ID NO: 8); and a light chain CDR3 comprising QQSREYPYT (SEQ ID NO: 9), ii) a humanized antibody or antigen binding fragment thereof that specifically binds the human folate receptor 1 comprising the heavy chain variable domain of SEQ ID NO: 4, and the light chain variable domain of SEQ ID NO: 10 or SEQ ID NO: 11, iii) a humanized antibody or antigen binding fragment thereof that specifically binds the human folate receptor 1 comprising the heavy chain of SEQ ID NO: 6 and the light chain of SEQ ID NO: 12 or 13, or iv) a humanized antibody or antigen binding fragment thereof comprising a heavy chain encoded by the plasmid DNA deposited with the ATCC on April 7, 2010 and having ATCC deposit no. PTA-10772 and a light chain encoded by the plasmid DNA deposited with the ATCC on April 7, 2010 and having ATCC deposit no. PTA-10773 or 10774. is an antibody or antigen binding fragment; is a linker; and is a maytansinoid or a maytansinoid analog, i) a humanized antibody or antigen binding fragment thereof that specifically binds a human folate receptor 1, wherein the antibody or antigen binding fragment thereof comprises: (a) a heavy chain CDR1 comprising GYFMN (SEQ ID NO: 1); a heavy chain CDR2 comprising RIHPYDGDTFYNQKFQG (SEQ ID NO: 2); and a heavy chain CDR3 comprising YDGSRAMDY (SEQ ID NO: 3); and (b) a light chain CDR1 comprising KASQSVSF AGTSLMH (SEQ ID NO: 7); a light chain CDR2 comprising RASNLEA (SEQ ID NO: 8); and a light chain CDR3 comprising QQSREYPYT (SEQ ID NO: 9), (a) a heavy chain CDR1 comprising GYFMN (SEQ ID NO: 1); a heavy chain CDR2 comprising RIHPYDGDTFYNQKFQG (SEQ ID NO: 2); and a heavy chain CDR3 comprising YDGSRAMDY (SEQ ID NO: 3); and (b) a light chain CDR1 comprising KASQSVSF AGTSLMH (SEQ ID NO: 7); a light chain CDR2 comprising RASNLEA (SEQ ID NO: 8); and a light chain CDR3 comprising QQSREYPYT (SEQ ID NO: 9), ii) a humanized antibody or antigen binding fragment thereof that specifically binds the human folate receptor 1 comprising the heavy chain variable domain of SEQ ID NO: 4, and the light chain variable domain of SEQ ID NO: 10 or SEQ ID NO: 11, iii) a humanized antibody or antigen binding fragment thereof that specifically binds the human folate receptor 1 comprising the heavy chain of SEQ ID NO: 6 and the light chain of SEQ ID NO: 12 or 13, or iv) a humanized antibody or antigen binding fragment thereof comprising a heavy chain encoded by the plasmid DNA deposited with the ATCC on April 7, 2010 and having ATCC deposit no. PTA-10772 and a light chain encoded by the plasmid DNA deposited with the ATCC on April 7, 2010 and having ATCC deposit no. PTA-10773 or 10774.