Abstract: An electrical connector assembly for electrically connecting different type daughter board to a mother board, comprises a first connector housing, a second connector housing, a plurality of first contacts and a plurality of second contacts. The first connector housing includes a first slot for receiving one daughter board therein and a plurality of first passageways each receiving one first contact. The second connector housing integrally connected with said the first connector housing, includes a second slot for receiving another daughter board therein and a plurality of second passageways each receiving one second contact. A plurality of third passageways are defined between the slots wherein each third passageway consists of at least a first passageways and a second passageways in the structure thereof for receiving a first contact and a second contact which are alternately arranged.