The purpose of this investigation was to study the prevalence of and risk factors for androgen deficiency in middle-aged men in Hong Kong. A community-based, cross-sectional household survey was performed in Hong Kong on men aged 45 to 64 years. Demographics, lifestyle information (cigarette smoking, alcohol consumption, and physical activity), and symptoms previously defined for identifying those with androgen deficiency were measured by using standardized questionnaires. Blood samples were collected in the morning, and total, free, and bioavailable testosterone levels were assessed. Data on androgen deficiency were available for 252 men aged 45 to 64 years. Crude prevalence of androgen deficiency was 9.52%. Prevalence increased significantly with age. For risk factors, having a lower personal income and having a history of hypertension were independently associated with increased risk of having androgen deficiency (odds ratio, 3.72; confidence interval, 1.01-13.61; and odds ratio, 2.89; confidence interval, 1.06-7.91, respectively). The prevalence of androgen deficiency in Hong Kong Chinese is similar to that found in Caucasians by using a similar definition. From this age-specific prevalence cross-sectional data, it is estimated that there are approximately 68,775 Hong Kong Chinese men aged 45-64 years with androgen deficiency. Future studies with large sample size are needed to evaluate the risk factors for androgen deficiency in men.