A model of individual differences that moderate attitude-behavior consistency was developed and tested in the context of predicting use consistency of the diaphragm. Variables hypothesized to moderate the attitude-behavior relationship included reactions to major life changes, the attitudes and opinions of others, sexual interest, locus of control, and the perceived susceptibility to pregnancy. Attitudes were conceptualized in terms of a Relative Contraceptive Utility (RCU), which was defined as the difference between the attitude toward the diaphragm and the attitude toward becoming pregnant. Women (N = 110) who attended family planning clinics in the New York Qty area and who used the diaphragm for an 8-month period were interviewed in the context of a 3-wave panel design. A threshold function between RCU and behavior was observed, such that when RCU was above an empirically derived cutoff, women tended to use the diaphragm consistently over an 8-month period. For women with RCUs below the cutoff, attitudes were unrelated to behavior. Inconsistency of diaphragm use for these latter women was best predicted by negative reactions to close friends' experiences with the diaphragm, low levels of perceived susceptibility to pregnancy, alcohol consumption, concern about becoming too old to have children, a preference for nonromantic sex, and the partner's unwillingness to refrain from sex if the women was not prepared.