Several studies have implied a potential inhibitory effect of smoking on the development of clinical benign prostatic hypertrophy (BPH). None of these studies compared gland size and smoking habits. We prospectively test the hypothesis that the identified "negative risk factor" that cigarette smoke has on the development of clinical BPH is mediated through inhibition of gland growth. One hundred and ninety-five men underwent transrectal ultrasonography with prostate volume calculations. A self-administered questionnaire detailing smoking habits was completed by the subjects. Correlations were looked for between various smoking habit parameters and gland size. Prostate gland size did not differ between current smokers, ex-smokers, and never smokers. Prostate volume did not correlate with smoking years (duration of exposure), nor with intensity of exposure (cigarette packyears). Smoke-mediated changes in enzymatic and endocrine pathways that regulate prostatic growth have been well documented. However, whatever "protective" effects smoke may have on BPH, they are not mediated via direct inhibition on gland growth. Alternatively, cigarette smoke may be involved in changing the dynamic component of BPH. Further testing, with special emphasis on irritative and obstructive symptoms, may help elucidate this possibility.