Enzyme activities were determined in fibroblast cell cultures of eight patients suspected of having a type of sphingolipidosis. The patients were 0 to 4 years of age; four were female and four were male. Thirteen age-matched controls were also included in the study. In one of the cases, hexosaminidase A activity was found to be 0% (43-82%), while in two other cases beta-galactosidase activity was found to be 5 nmol/h/mg protein (100-1035 nmol/h/mg protein) and arylsulfatase activity was found to be 12 nmol/h/mg protein (106-990 nmol/h/mg protein), respectively. Two more enzymes, alpha-galactosidase (11-39 nmol/h/mg protein) and cerebroside beta-galactosidase (3.7-6.9 nmol/h/mg protein), were also evaluated but were found to be in the normal ranges in these patients. Therefore, these patients were considered to have Tay-Sachs disease, GM1 gangliosidosis and metachromatic leukodystrophy, respectively. The remaining five patients were normal in respect to the five enzyme activities determined. For the prenatal diagnosis of metachromatic leukodystrophy, arylsulfatase A activity was determined in one amniotic cell culture. The activity found in this case was lower than normal (34 nmol/h/mg protein versus 387 nmol/h/mg protein found in three control amniotic cell cultures.