Intrabiliary administration of Triton X-100 is of interest in producing effects on biliary tree permeability and canalicular biliary excretory function. Treatment with 0.4% Triton (40 microliter) was shown to increase the biliary excretion of intraportally administered [3H]sucrose. It also decreased recovery of [3H]sucrose given into the biliary tree. Thus, we concluded that Triton treatment increased biliary tree permeability. Using a different set of marker compounds, canalicular transport of bromphenol blue, [14C]morphine glucuronide and [3H]ouabain was found to be decreased. The fact that [3H] taurocholate excretion into bile was not affected whereas that of [3H]ouabain was lends support to the concept that taurocholate and ouabain are not transported by a common pathway.