Venous tolerance of a new water soluble polyene antibiotic, SPK-843, in 5% glucose solution for infusion is low in laboratory animals. The use of Intralipid 10% emulsion was therefore proposed, in which the antibiotic remained chemically stable for at least 2 h in a mildly acid or nearly neutral environment and at concentrations of 0.1-0.5 mg/mL, producing no alterations in the emulsion structure. Tolerance was assessed through repeated infusions in the ear marginal vein of rabbits and was found much more satisfactory than the tolerance observed when the vehicle used was 5% glucose solution. The study of the effect of some variables (concentration, volume infused, dose per kg) on venous toxicity offered the possibility to plan optimal administration conditions of presumed therapeutic doses.