Abstract Intracellular α- l-fucosidase and hexosaminidase showed similar isoelectrofocusing patterns in control, cystic fibrosis and neuraminidase-deficient fibroblasts and were unaffected by neuraminidase treatment. An I-cell strain excreted these two enzymes at 3–4 times the rate of the three other cell types. I-cell and neuraminidase-deficient cells excreted more of the electronegative forms of these enzymes than control and cystic fibrosis cells. Extracellular hexosaminidase A and B were both sensitive to neuraminidase for the four cell types. Extracellular α- l-fucosidase consisted of a pH 6.1 form insensitive to neuraminidase and other forms that were sensitive and changed to a pI 7.0–7.1 form. Cystic fibrosis extracellular a- l-fucosidase and hexosaminidase behaved as for control fibroblasts.