ObjectivesAdverse effects of antiviral therapy are among the main threats to adherence and quality of life for HIV patients. Understanding their impact requires a better knowledge of their subjective significance. With this aim in view, the study of the relationship between defense mechanisms and pain-related side effects is proposed. Material and methodSixty-three subjects (43 men, 20 women) completed the Defense Style Questionnaire and a rating scale evaluating adverse effects of antiretroviral therapy. Results(1) for the entire sample, correlations between pain-related side effects and passive-aggression (r=.42, P<01), splitting (r=.28, P<05), displacement (r=.25, P<05), acting out (r=.45, P<01), projection (r=.43, P<01), autistic fantasy (r=.38, P<01) and somatization (r=.48, P<01); (2) No significant differences concerning pain-related side effects are observed according to gender; (3) differences by gender are observed regarding the correlations between defenses and pain-related side effects. As regards to women, twelve out of the twenty defenses assessed by the DSQ are significantly correlated with pain-related side effects (aggression, undoing, splitting, devaluation, reaction formation; isolation; acting out, projection, rationalization; autistic fantasy; somatization; sublimation). Globally, correlations are strong between these two dimensions (r>.50 for 10 defenses). For men, only 5 defenses are significantly correlated with pain-related side effects (aggression, acting out; projection, repression, somatization). These correlations are descriptively smaller than those observed in women (r≤.40). Significant differences between correlations are found by gender for undoing (z=2.09, P<.05), devaluation (z=2.33, P<05), reaction formation (z=2.32, P<05) and rationalization (z=3.49, P<01). These results emphasize the subjective dimension of treatments side effects. They suggest that, when faced with adverse effects, women are more solicited at the defensive level than men. It could also suggest that the threat of adverse effects is different depending on the gender of subjects: It affects a broad range of domain for women whereas for men, this threat is more sectorised, essentially impacting interpersonal relationships. ConclusionFurther researches should study interactions between gender, treatments side effects and defensive functioning.