The present invention relates to the use of known and novel compounds as inhibitors of UDP-GlcNAc:Gal.beta.1,3GaINAc-R (GlcNAc to GalNAc) .beta.1,6-N-acetylglucosaminyl transferase (core 2 .beta.1,6 N-acetylaminotransferase, core 2 GlcNAc-T-EC 2.4.1.102). Such inhibitors have applications in therapy for diseases associates with raised activity of core 2 GlcNAc-T, in particular inflammatory diseases, atherosclerosis, diabetic cardiomyopathy, cancers--including treatment or prevention of metastasis--or diabetic retinopathy.