The tissue distribution kinetics and elimination of 4,4'-methylene bis(2-chloroaniline) (MBOCA) in rats was studied after a single dose of [14C]MBOCA (0.49 mg/kg body weight, i.v.). The highest concentrations of radioactivity were in the small intestine, liver, adipose, lung, kidney, skin, and adrenals. For most tissues, a rapid decrease in radioactivity was followed by a slower decrease except for the small intestine, adipose and skin which demonstrated transient increases. Subcellular distribution in liver at 1 h showed radioactivity in all cell fractions. Although very lipophilic, [14C]MBOCA was completely eliminated within 48 h with the major route via the feces (73.4%).