OBJECTIVE The purpose of this study was to investigate whether alpha-galactosidase activity is present in whole and glandular saliva and whether alpha-galactosidase activity depends on blood type and secretor status. METHODS For the first experiments, 30 healthy participants (15 men, 15 women; mean age, 24.2+/-1.5 years) who were 10 A, 10 B, and 10 O blood type subjects were included. alpha-Galactosidase activity in unstimulated whole saliva (UWS) was assayed by using 4-methylumbelliferyl-alpha-d-galactopyranoside as a substrate. Total protein concentration was determined by bicinchoninic acid assay. The secretor status of the blood group antigens was determined by immunoblotting. alpha-Galactosidase activity in UWS according to gender, blood type, secretor status, sample clarification, and buffer was investigated. Daily variations of alpha-galactosidase activity and alpha-galactosidase isozyme activity were also investigated. For the second experiments, 10 healthy blood type B participants (5 men, 5 women; mean age, 27.0+/-2.7 years) were enrolled. alpha-Galactosidase activity in whole and glandular saliva was investigated. RESULTS alpha-Galactosidase activity was detected in UWS and was mainly isozyme A activity. There was no difference in alpha-galactosidase activity according to gender, blood type, and secretor status. alpha-Galactosidase activity in UWS was higher in unclarified samples than in clarified ones and showed wide daily variations. alpha-Galactosidase activity in whole saliva was significantly higher than that in glandular saliva. CONCLUSIONS alpha-Galactosidase activity which is mainly isozyme A activity was detected in human whole and glandular saliva. alpha-Galactosidase activity in UWS did not differ according to blood type and secretor status.