An electrical connector assembly (10, 110) having balanced impedance and shielding, the electrical connector assembly (10, 110) comprising: a first connector housing having first modules positioned therein, the first modules having first mating ends and first mounting ends, the first modules having first surfaces and oppositely facing second surfaces, signal pathways provided on the first surfaces, the signal pathways being arranged in differential pairs, first ground pathways provided on the first surfaces and extending from the first mating ends to the first mounting ends, each of the first ground pathways positioned adjacent the signal pathways, second ground pathways provided on the first surfaces, the second ground pathways positioned between side edges of the first modules and respective signal pathways of the signal pathways; a second connector housing having second modules positioned therein, the second modules having second mating ends and second mounting ends, signal contacts positioned in the second modules, the signal contacts extending between the second mating ends and the second mounting ends, the signal contacts being arranged in pairs to carry differential signals, first ground contacts positioned in the second modules, the first ground contacts extending between the second mating ends and the second mounting ends, the first ground contacts being positioned adjacent to respective signal contacts of the signal contacts, second ground contacts positioned in the second modules, the second ground contacts positioned between side surfaces of the second modules and respective signal contacts of the signal contacts; characterized in that a module engaging section of a first ground connector contact positioned proximate the side edges of the modules has slots for receiving the side edges of the module, respective slots of the slots having contact projections which extend into the respective slots to make a mechanical and electrical engagement with the second ground pathways positioned on the first surfaces of the modules. a first connector housing having first modules positioned therein, the first modules having first mating ends and first mounting ends, the first modules having first surfaces and oppositely facing second surfaces, signal pathways provided on the first surfaces, the signal pathways being arranged in differential pairs, first ground pathways provided on the first surfaces and extending from the first mating ends to the first mounting ends, each of the first ground pathways positioned adjacent the signal pathways, second ground pathways provided on the first surfaces, the second ground pathways positioned between side edges of the first modules and respective signal pathways of the signal pathways; a second connector housing having second modules positioned therein, the second modules having second mating ends and second mounting ends, signal contacts positioned in the second modules, the signal contacts extending between the second mating ends and the second mounting ends, the signal contacts being arranged in pairs to carry differential signals, first ground contacts positioned in the second modules, the first ground contacts extending between the second mating ends and the second mounting ends, the first ground contacts being positioned adjacent to respective signal contacts of the signal contacts, second ground contacts positioned in the second modules, the second ground contacts positioned between side surfaces of the second modules and respective signal contacts of the signal contacts; characterized in that a module engaging section of a first ground connector contact positioned proximate the side edges of the modules has slots for receiving the side edges of the module, respective slots of the slots having contact projections which extend into the respective slots to make a mechanical and electrical engagement with the second ground pathways positioned on the first surfaces of the modules.