BACKGROUND. The objective of this work was to determine the effect of an androgen agonist, R1881, on intracellular cholesterol synthesis and esterification in androgen-sensitive (AS) prostate cancer (LNCaP) cells. METHODS. We investigated the activity and expression of cholesterol metabolism enzymes, HMG-CoA-reductase and ACAT in the LNCaP and PC-3 (androgen-independent control) models. RESULTS. Microsomal PC-3 HMG-CoA-reductase activity was increased with R1881 despite having similar cholesterol levels while increased cholesterol levels in microsomes from LNCaPs treated with R1881 (Lþ) were associated with increased HMG-CoA reductase activity. Increased intracellular cholesteryl esters (CE) found in (Lþ) were not associated with an increased ACAT1 activity. There was no effect from androgen treatment on ACAT1 protein expression in theses cells; however, ACAT2 expression was induced upon R1881 treatment. In contrast, we found an increase in the in vitro ACAT1 activity in PC-3 cells treated with androgen (Pþ). Only ACAT1 expression was induced in Pþ. We further assessed the expression of STAT1a, a transcriptional activator that modulates ACAT1 expression. STAT1a expression and phosphorylation were induced in Pþ. To determine the role of the AR on ACAT1 expression and esterification, we treated PC-3 cells overexpressing the androgen receptor with R1881 (PARþ). AR expression was decreased in PARþ cells; ACAT1 protein expression and cholesterol ester levels were also decreased, however, ACAT2 remained unchanged. STAT1a expression was decreased in PARþ. CONCLUSIONS. Overall, these findings support the importance of cholesterol metabolism regulation within prostate cancer cells and unravel a novel role for STAT1a in prostate cancer metabolism.