Vasectomy has been shown to affect the pattern of mRNA expression of P34H, a human sperm protein added to the acrosomal cap during epididymal transit. It has been reported that vasectomy alters the histology of the reproductive tract in various species as a result of the increased pressure in the epididymis. The aim of this study was to evaluate if other epididymis-specific mRNAs, which are expressed in different patterns along the duct, are altered by vasectomy as well. We analyzed the expression of P31m (a monkey homologue of human P34H) and three different HE-like (HE-l) mRNAs along the epididymis in the cynomolgus monkey (Macaca fascicularis). Sexually mature cynomolgus monkeys were vasectomized unilaterally; then the epididymides were surgically removed at different time points. The ipsilateral normal epididymis was used as a control. Histomorphometric measurements showed that the height of the epididymal epithelial cells started to be affected only at 14 wk postsurgery. However, Northern blot and in situ hybridization analysis showed that the expression pattern of P31m, HE1, and HE5-like mRNA along the epididymis was not affected by vasectomy. Only the HE2-like mRNA predominantly expressed in the normal corpus epididymidis was significantly lowered 14 wk after vasectomy. Thus, ductal obstruction differentially alters mRNA expression along the epididymis of the cynomolgus monkey.