We assessed the influence of a "video doctor's" affective communication style (warm vs. neutral) and of a preamble to questions about sexual activity on patients' disclosure of risky sexual behavior and injectable drug use. To isolate the effects of the independent variables, we created an interactive multimedia program for HIV risk assessment using a video doctor portrayed by an actor. Participants were assigned to one of four conditions: no preamble and a neutral physician, no preamble and a warm physician, a preamble and a neutral physician, or a preamble and a warm physician. Almost 60% of a convenience sample of 393 subjects reported engaging in two or more risky behaviors. Disclosure of risky behaviors was not significantly affected by the preamble. A warm communication style elicited more disclosure than a neutral style, suggesting that physicians' communication style is important in determining how much sensitive information patients are willing to reveal.