Abstract 1. 1. The levels and properties of microsomal glycoprotein galactosyltransferase of cultured skin fibroblasts from control and cystic fibrosis patients were investigated using bovine submaxillary gland mucin as the exogenous acceptor. 2. 2. Although the mean specific activity of this enzyme was higher in cystic fibrosis fibroblasts, the difference was not significant. 3. 3. The properties of the enzyme as regards pH optimum, metal ion and Triton X-100 requirement, apparent K m , heat stability and nucleotide/sugar-nucleotide response were similar for control and cystic fibrosis fibroblasts.