The adsorption of diazepam to infusion sets and plastic syringes was studied. Infusion solutions consisting of diazepam injection (Valium) in glucose 5.5%, or diazepam emulsion in a lipid emulsion (Intralipid 10%) were infused through two different infusion sets (Transcodan L-74 and Cutter IL). It was found that, when an infusion solution with a low diazepam concentration (0.04 mg/ml) was infused slowly (4 ml/h), the diazepam adsorption was more than 80%. At a higher diazepam concentration (0.1 mg/ml) and increased infusion rate (20ml/h) the adsorption decreased. Diazepam injection in glucose 5.5% was adsorbed to a higher degree (40-75%) than diazepam emulsion in glucose 5.5% (15-35%). When diazepam emulsion was diluted with the lipid emulsion, no diazepam adsorption to the infusion set occurred at this concentration and infusion rate. No significant difference between the two infusion sets could be found. The miscibility of diazepam emulsion with glucose 5.5%, glucose 10%, or sodium chloride 0.9% was examined. Diazepam emulsion proved to be miscible with glucose 5.5% and glucose 10%, but sodium chloride should not be used to dilute diazepam emulsion. The effect on the diazepam concentration of storing diazepam injection and diazepam emulsion in plastic syringes for up to 4h was also studied. It was found that the diazepam concentration remained unchanged during this time.