alpha1-Adrenergic receptors (alpha1ARs) are G protein-coupled receptors important in the dynamic component of benign prostatic hyperplasia. alpha1ARs stimulate predominantly phospholipase C-beta, resulting in mobilization of calcium from intracellular stores and, ultimately, smooth muscle contraction. cDNAs encoding three human alpha1ARs (alpha1a, alpha1b, alpha1d) have been cloned, expressed stably in cells, and characterized pharmacologically. Extensive species heterogeneity in tissue distribution emphasizes the importance of studying alpha1ARs in human tissues. Because of the important role of alpha1aARs in mediating prostate smooth muscle contraction, this current review describes alpha1a carboxyl terminal splice variants, examines alpha1AR subtype distribution in various tissues and the role of the putative alpha1LAR in human prostate, provides a brief discussion regarding regulation of this receptor by agonist, and finally discusses implications of distinct alpha1AR subtype distribution in human bladder compared with prostate.