Local venous reactions during and after i.v. injections of three different formulations of diazepam were studied in 200 patients undergoing gastroscopy. Of the patients receiving diazepam in propylene glycol (Stesolid) 78% experienced pain on injection and 48% subsequently developed clinical evidence of thrombophlebitis. The figures for Stesolid MR (diazepam in Cremophor EL) were 38% and 9% respectively. A significant decrease was achieved (pain on injection 1%; clinical thrombophlebitis 4%) when using Diazemuls, a new formulation in which diazepam is dissolved in oil and emulsified in water. Since no difference in the therapeutic effect of the different formulations was observed, Diazemuls represents a clear advantage to Stesolid and Stesolid MR.