1. Sialyl- and galactosyl-transferase activities were determined in wild type and conA-resistant L6 rat myoblasts with substrates derived from fetuin, alpha 1-acid glycoprotein and bovine submaxillary mucin; fetuin was the best acceptor for both enzyme activities, whereas the mucin did not act as an acceptor. 2. The optimum pH for sialyltransferase was 6.6 in both cell lines. 3. The optimum pH for galactosyltransferase in the wild type cell line was 6.2 which was slightly higher than the value of 5.8 found for the conA-resistant cells. 4. Values for Km for both enzyme activities increased five to ten-fold in the variant cell line with both acceptors. 5. The main sialyltransferase activity was the Gal beta 1----4GlcNAc alpha 2----3sialyltransferase for N-linked chains. The galactosyltransferase was most likely the enzyme that is responsible for the synthesis of the Gal beta 1----4GlcNAc structure.