For about 30 years, soon after the onset of the AIDS epidemic, sexual-health messaging has emphasized personal responsibility for using condoms to protect from acquiring or transmitting HIV or other sexually transmitted infections. Those who did not use condoms during casual sexual encounters may therefore feel compelled to offer to others aware of their behavior what sociologists have called “accounts,” an impression-management strategy to avoid unfavorable judgment. We analyzed accounts—excuses and justifications—from qualitative interviews with 150 adults who had unprotected sex in the past 3 months with at least two different partners met online (ages 18-50, mean: 33.7, equally divided among black, Hispanic, and white men and women, over half were college educated and the median yearly household income range was $50-$75,000). Many participants made excuses that aimed to defer responsibility for unprotected sex: they claimed that consistently practicing safer sex was impossible, that they got carried away by sexual passion, that they were inebriated, that they were influenced by emotional or psychological problems, or they put fault on their partners. Participants also provided justifications, claiming that unsafe sex had been acceptable because the risks taken were likely minimal or negotiated with their partner. Understanding the accounts heterosexual adults offer to excuse and justify condomless sex with partners met online can be helpful in developing prevention messages that debunk these explanations for their behavior.