The neuroendocrine cells (NCs) in the peripheral prostatic zone of 32 patients without prostatic symptoms and with an average age of 61.4 +/- 6.7 (range 48-75) years were studied, and it was found that most are closed-type cells (95.8%) and that there is a gradual fall both in their total number and the number per square millimeter (p = 0.03) with advancing age. There were microscopic foci of high-grade prostatic intraepithelial neoplasia (PIN) in 59.3% of the patients and occult carcinomas in 28.1%, but no statistical relationship was found between these lesions and the number of NCs (p = 0.35 and p = 0.9, respectively). The gradual increase in NCs in the peripheral zone of normal prostates as of adolescence, reported in the literature, would appear to support a possible androgenic action on these cells. Our finding of a decrease in patients with foci of PIN and carcinoma from the fifth decade suggests that this decrease in NCs may make the prostate more susceptible to carcinogenic factors.