Measurement of weight and height in 179 adult psychiatric patients, ages 17-70 years attending out patient clinics for receiving their antipsychotic drugs in the Southwestern Saudi Arabia were made. Body mass index (BMI = Kg/m²) was used for assessment of clinically relevant obesity. The overall prevalence of obesity was 20.7 %. Obesity was nearly six times greater in female patients (59%) than in male patients (10%). Statistical analysis showed that both age and unemployment were significantly associated with increase in the risk of clinically relevant obesity (Odds ratio, 95% confidence interval: 1.03 [1.0-1.068] and 0.419 [0.181-0.970] respectively) while duration of treatment was not (P < 0.65) (Odds ratio, 95% confidence interval: 1.021 [0.933-1.117]. In view of these findings, engaging patients in regular jobs and introducing health Education programmes that encourage physical activity as strategy directed towards weight reduction in patients taking antipsychotic drugs will certainly be justifiable.