The transformation of a single-sex college into a coeducational college can be extremely costly. However, a cooperative arrangement among colleges, such as the one described in this paper, can sexually integrate single-sex colleges at very little extra cost. The Five Colleges Cooperation consists of 1 male college, Amherst; 2 female institutions, Smith and Mount Holyoke; a new coeducational undergraduate college, Hampshire College; and a large state university, the University of Massachusetts. In this cooperative agreement, any student at any one of the colleges may elect to enroll in any course at any other of the colleges, so long as that course is not offered at his or her own institution. The possibility of establishing student centers for students at all of the colleges has also been discussed, as well as joint extra-curricular organizations and social clubs. This arrangement, which would cost the colleges approximately $10 million if undertaken separately, can be achieved for about $200,000 a year in a cooperative arrangement. (HS)