The percutaneous absorption of an organosilicon quaternary ammonium chloride (14C)-3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride (14C-Si-QAC) was studied in rabbits. Aqueous solution of 14C-Si-QAC was either applied to the intact, clipped back of animals for 10 days or administered by a single intravenous dose. Urine and feces were collected at 24-h intervals and tissue concentration of radioactivity was determined at the end of the 10-day study period. Elimination of 14C-Si-QAC after parenteral administration was slow and occurred by both urine and feces (13.5% in urine and 20% in feces). No radioactivity was found in the urine of dermally treated animals. Tissue concentrations of 14C were highest in the liver, lung and kidneys after i.v. administration. None was detected in tissues of dermally treated animals. The results showed that the absorption of 14C-Si-QAC through the skin of the rabbit was essentially zero. The potential absorption hazard of the use of this antimicrobial agent in contact with the skin is therefore considered to be insignificant.