This study assesses the efficacy of an educational and dietary approach in preventing olanzapine-induced weight gain. Eighteen patients affected by schizophrenic disorders were treated with olanzapine and weighed twice-weekly for 24 weeks. A psychoeducational intervention and referral to a nutritionist was introduced from the beginning of olanzapine treatment in 9 patients, and from the 9th week of therapy in 8 patients. Results showed that after 8 weeks of olanzapine treatment, weight gain was contained in the subjects receiving intervention unlike patients without preventive intervention (+0.99+/-3.34 kg vs. +2.96+/-3.08 kg; p<.03). At the end of the trial these patients partly shed their gain (-1.77 kg), presenting a final weight which was not significantly different from baseline (+1.19 kg). Subjects receiving the psychoeducational approach from the beginning were significantly heavier than at baseline (+3.4 kg). Poor dietary compliance correlated significantly with an increase in body weight, while higher mean dosages of olanzapine correlated with better weight-gain control.