An electrical connector comprising: a housing, and a plurality of contact modules in said housing, wherein each contact module comprises a mating edge and a mounting edge, each mating and mounting edge having a row of contacts (82, 86) including signal contacts and ground contacts, each mating edge contact being electrically connected to a corresponding mounting edge contact by signal conductors (106a, 106b, 206a, 206b) and ground conductors (104, 204) extending along a predetermined path within said contact module to form a lead frame (100, 200) in each contact module, said ground conductors (104, 204) and signal conductors (106a, 106b, 206a, 206b) being arranged in an adjacent relationship to provide electrical shielding, and said signal conductors (106a, 106b, 206a, 206b) and ground conductors (104, 204) of several contact modules being arranged, when seen in a cross-sectional view through the lead frames, in an array having outer and inner layers, wherein at least a portion of the signal conductors (106a, 106b) and ground conductors (204a, 204b) in the outer layers has a width (w1, w2) transverse to said predetermined path that is different from a width transverse to said predetermined path of the signal conductors and ground conductors in the inner layers; the electrical connector being characterized in that said signal conductors (106a, 106b, 206a, 206b) and ground conductors (104, 204) are arranged in one of a first and second pattern, adjacent contact modules in said housing have a different one of said first and second patterns, said first and second patterns each including pairs of signal conductors (106a, 106b, 206a, 206b) and individual ground conductors (104, 204) arranged in an alternating sequence, and each said ground conductor (104, 204) has a width transverse to said predetermined path that is substantially equal to a combined transverse width (L') across a pair of signal conductors (106a, 106b, 206a, 206b) in an adjacent contact module, said ground conductor (104, 204) thereby shielding said pair of signal conductors (106a, 106b, 206a, 206b) in said adjacent contact module. a housing, and a plurality of contact modules in said housing, wherein each contact module comprises a mating edge and a mounting edge, each mating and mounting edge having a row of contacts (82, 86) including signal contacts and ground contacts, each mating edge contact being electrically connected to a corresponding mounting edge contact by signal conductors (106a, 106b, 206a, 206b) and ground conductors (104, 204) extending along a predetermined path within said contact module to form a lead frame (100, 200) in each contact module, said ground conductors (104, 204) and signal conductors (106a, 106b, 206a, 206b) being arranged in an adjacent relationship to provide electrical shielding, and said signal conductors (106a, 106b, 206a, 206b) and ground conductors (104, 204) of several contact modules being arranged, when seen in a cross-sectional view through the lead frames, in an array having outer and inner layers, wherein at least a portion of the signal conductors (106a, 106b) and ground conductors (204a, 204b) in the outer layers has a width (w1, w2) transverse to said predetermined path that is different from a width transverse to said predetermined path of the signal conductors and ground conductors in the inner layers; the electrical connector being characterized in that said signal conductors (106a, 106b, 206a, 206b) and ground conductors (104, 204) are arranged in one of a first and second pattern, adjacent contact modules in said housing have a different one of said first and second patterns, said first and second patterns each including pairs of signal conductors (106a, 106b, 206a, 206b) and individual ground conductors (104, 204) arranged in an alternating sequence, and each said ground conductor (104, 204) has a width transverse to said predetermined path that is substantially equal to a combined transverse width (L') across a pair of signal conductors (106a, 106b, 206a, 206b) in an adjacent contact module, said ground conductor (104, 204) thereby shielding said pair of signal conductors (106a, 106b, 206a, 206b) in said adjacent contact module.