Effects of some proteases, phospholipases and a neuraminidase on the Ca2+-receptor of the frog tongue were studied by recording neural responses from single fungiform papilla preparations before and after application of the enzymes. The results obtained were as follows: 1) Trypsin, α-chymotrypsin, pronase and high concentrations of phospholipase-C inhibited the Ca2+-response of the receptor irreversibly. 2) Ficin, phospholipase-D and low concentrations of phospholipase-C inhibited the Ca2+-response temporarily, and the response recovered 10 to 20 min after removal of theenzymes. A similar temporal inhibition was produced by neuraminidase, but the recovery was more gradual than in the cases of ficin and phospholipases. 3) Phospholipase-A hardly produced any significant effects on the Ca2+-response. Based on these results, the characteristics of the Ca2+- receptor of the frog tongue were considered.