OBJECTIVE: Describe influence of relationship characteristics and quality, reasons for sex, number of partners, and potential consequences of STD communication with partners on STD-communication self-efficacy (CSE).DESIGN: Cross-sectional study of adolescents (mean age=18.1; range=14-21 years) with genital infection or known contact to C. trachomatis, N. gonorrhoeae or T. vaginalis. Subjects were enrolled at the time of initial treatment. Data were collected by individual interviews with research assistants. The outcome variable was a 3-item scale composed of measures of perceived capability to talk to the partner about the STD, discuss the need to take medicine, and check if the partner had been treated (scale range 3-12, with higher scores indicating greater self-efficacy; Cronbach's α=0.85). Predictor variables were number of partners in the last 2 months, anticipated negative consequences of discussing STD with a partner (2 items; α=.67), emotion-based reasons for sex (3 items; α=0.77), sexual reasons for sex (3 items; α=.73) and a 4-item scale assessing relationship quality and comfort (α=0.89).RESULTS: 111 subjects (75 women and 36 men) completed interviews. Average number of sex partners in the previous 2 months was 1.4 and 2.4 for women and men, respectively (p<0.05 by t-test). Average STD CSE score was 8.8 (SD=2.3), with no significant gender difference. STD CSE was correlated with number of partners in the previous 2 months (r=-0.18), anticipated negative consequences of discussing STD (r=-0.4), and more positive relationship quality (r=0.48), but not with emotional or sexual reasons for sex. In multiple linear regression analyses (controlling for gender), STD CSE was independently (p<0.05) related to number of partners (β=-0.26) and to a more positive assessment of relationship quality (β=0.43). This model accounted for 42% of the variance in STD CSE.CONCLUSIONS: Improved prevention of STD reinfections may require increased attention to qualitative aspects of the interpersonal relationship that influence communication with sex partners about treatment.