Apparatus for sorting and orienting sperm cells has a pair or walls in confronting relationship forming a flow chamber having inlet, a downstream outlet, and intermediate detector region. The inlet receives first and second spaced apart streams of input fluid and a third stream of sample fluid containing the cells to be sorted. The first and second streams have respective flow rates relative to third stream, such that the third stream is constricted forming a relatively narrow sample stream, so that the cells are oriented parallel to the walls. A detector detects desired cells and a sorter downstream of the detector for sorting the desired cells from the stream.