Three glycoforms of alpha 1-acid glycoprotein (AGP) were biotinylated to examine their binding in mouse testis by light microscopy. The transition from one stage to another in the spermatogenic cycle is marked with an appearance of a receptor for the Concanavalin A (Con A) non-reactive glycoform AGP-A in the cytoplasm of spermatocytes, young spermatids and Sertoli cells. This receptor disappears in the late stages of the spermatids. The Con-A intermediately reactive and the Con-A reactive glycoforms, AGP-B and AGP-C, showed weak reaction in the cytoplasm of spermatocytes, spermatids and Sertoli cells and, at the last stages in the spermatogenic cycle, a very strong reaction in the late elongated spermatids and the apical extensions of Sertoli cells. The interactions are lectin-like as confirmed by inhibition with simple sugars. In addition, the bindings were inhibited by steroid hormones. AGP-A was inhibited by testosterone, oestradiol and progesterone, while AGP-B and AGP-C were inhibited by mannose, GlcNAc, cortisone, aldosterone, oestradiol and progesterone. The receptors and the corresponding AGP glycoforms may be adhesion molecules between Sertoli cells and the spermatogenic cells and may have a function as a regulatory factor for spermatozoa development.