To compare the effects of two inocula on the induction of amyloidosis in normal and thymectomized ducks, 180 normal and 50 thymectomized ducks were injected intravenously weekly for up to 16 weeks with either crude endotoxin or crude whole cell extract of a virulent strain of Escherichia coli (O78), and another 60 ducks were injected with normal saline as study control. During the first 5 weekly injections, the initial doses of inducing agents were the smallest and then adjusted upward to the maximum study doses (1 or 2 mg/bird of crude endotoxin and 15-18 x 10(8) bacteria/bird of crude whole cell extract), which were then maintained over the course of the study. The incidence of amyloid deposition were: 50.00% (25/50) for thymectomized ducks that received 1 mg/bird/week of crude endotoxin, 61.67% (37/60) for intact ducks that received 15 x 10(8)-18 x 10(8) bacteria (crude whole cell extract)/bird/week, 53.33% (32/60) for intact ducks received 2 mg/bird/week of crude endotoxin, and 63.33% (38/60) for intact ducks received 1 mg/bird/week of crude endotoxin. The results suggest that crude whole cell extract and crude endotoxin induced amyloidosis in ducks at similar rates and that, in ducks, thymectomy has no appreciable effect on the occurrence of amyloidosis.