This multi-center contraceptive effectiveness and safety study of the SILCS diaphragm will enroll approximately 450 couples at risk for pregnancy w at six study sites in the U.S. The study will randomly assign approximately 300 couples to use the SILCS diaphragm with BufferGel (BG) and approximately 150 couples to use the SILCS diaphragm with Gynol II (2% N-9 gel). At two sites, a substudy involving colposcopy and microflora will be conducted in about 80 women (40 at each site). For certain evaluations, the data from a contraceptive study conducted by NICHD of the Ortho All-Flex diaphragm used with either BG or N-9 will be used as historical controls.