This qualitative study examined how adolescents conceptualize sexual behavior. Open-ended interviews about sex were conducted with a sample of 21 male and 18 female African- American adolescents. Topics related to health risk virtually never emerged in their responses. The topic of partner infidelity and concerns about control of infidelity, on the other hand, were mentioned extensively. Informants described a cycle in which commitment to a partner often leads to suspicion of infidelity and jealousy. The jealous partner then performs acts of surveillance which can lead either to reassurance or to discovery of infidelity. The article concludes by discussing the degree of uniqueness of fidelity management to African- American adolescents and possible relevance to design of AIDS risk-reduction interventions.