Multiple forms of neutral alpha-glucosidase were found in human urine. In a number of individuals three enzyme forms were detected, in other persons--four forms. The alpha-glucosidase I and 2 were present in urine as well as in kidney of some individuals, whereas in urine of other persons only alpha-glucosidase I was found. Both forms of neutral alpha-glucosidase I and 2 from human urine exhibited the maximal activity at pH 5.75 = 6.5, had a similar Km value (0.73 mM) with maltose as a substrate and did not differ in their properties from the corresponding forms of neutral alpha-glucosidase in a soluble fraction from human kidney.