The effect of thyroidectomy on phosphohexoseisomerase (PHI) and lactate dehydrogenase (LDH) activities in the seminal vesicles and ventral prostate of rats has been investigated. Following long term thyroidectomy the activities of PHI and LDH declined 28% and 40%, respectively, in the ventral prostate when compared to the values for normal rats. However, both PHI and LDH activities were elevated to 27% and 33%, respectively, in the seminal vesicles of thyroidectomized rats. The data reported in this communication are consonant with the view that an altered thyroid state may have a definite influence on androgen‐regulated glycolytic enzyme activities in the male accessory organs, thereby indirectly affecting the secretory activities of these tissue