Objective: To investigate both the possible changes induced by acute alcohol intake on prostate tissue at the ultrastructural level and its effect on serum prostate-specific-antigen (PSA)-like protein levels in rats. Materials and Methods: 44 male Wistar rats were included in the study in four separate groups; 7 treatment and 4 control animals were selected for each group. The treatment group received 40% ethanol ( 6 g/ kg) while the control group was injected with the same dose of intraperitoneal isotonic saline. The first group was sacrificed after 3 h, the second group after 24 h, the third group after 72 h and the fourth group on day 7. Samples were examined by light and Jeol-100 electron microscope. Total serum PSA-like protein levels were determined by a Tosoh immunoenzymometric analyzer AIA 600. Results: In groups 1-3, electron microscopy showed dilatations in the endoplasmic reticulum cisternae of prostatic acinar cells, disarrangements in apparent Golgi complex and apertures belonging to the basal labyrinth. It was also observed that there was a mass of debris cells inside the acinar lumen, and the secretory epithelium was detached from the basal membrane in some places. No pathology was found in group 4 by light and electron microscopy. In group 1, significant levels of increased serum total PSA-like protein were found compared to controls and other treatment groups ( p = 0.006). Conclusions: The fundamental effect of acute alcohol intake on prostate tissue was observed in intermediate stages participating in the exocrine secretion process in the cellular organelles. At the same time, this influences the levels of serum PSA-like protein. Copyright (c) 2005 S. Karger AG, Basel.