The purpose of this study is to explain the relationship between the pharmacological mechanism of levamisole and the cellular activity of cellular alkaline phosphatase (ALPase) in kidney cells. The results of our investigation were as follows. 1. Cellular ALPase activity in Macacus rhesus monkey kidney cells (MA 104 cells) and primary cultured rabbit kidney proximal tubular cells treated with levamisole was increased about two or three times than control. However, 50% of ALPase activity in cultured medium was inhibited by levamisole itself. 2. The proliferation of MA 104 and cultured rabbit kidney proximal tubular cells was linearly decreased in paralleled with increase of levamisole concentration $(50;and;500;{mu}M)$ with MTT test. 3. In the heat stability tests, the inhibition of ALPase activity with and without levamisole at $56^{circ}C$ in MA 104 cells showed different $IC_{50}$ values. 4. HPLC analysis of levamisole metabolites produced by cultured MA 104 cells suggested that the formation of a metabolite, that may be associated with its increase of cellular ALPase activity. Based on these results, we assumed that the increase of cellular ALPase activity by levamisole was evoked by modification of the ALPase catalytic sites.