This paper analyzes the modulating influence of some variables in the adherence to treatment in a group composed by 69 HIV infected patients attending Preventive Medicine Service at the General Hospital of Castellon (Spain). Adherence to treatment is defined by patient report about three aspects: change of risk behaviors since diagnosis was established, adherence to pharmacological treatment and attendance to medical appointments. Results show that variables related to previous history of sharing syringes for drug use, poor causal attribution of infection to risk behaviours, excessive optimism about seriousness of disease, lack of confidence in treatment, forgetfulness, use of maladaptative coping strategies and perception of poor information in physicians are statistically related to non-adherence to treatment. Other variables such as depression, perceived social support and relationship with physicians also seem to be important. However, none of the variables analyzed proved to have predictive value for adherence to treatment as obtained with logistic regression analysis.