The LD50 of sulfluramid topically applied to 2-d-old, fifth instars of the German cockroach, Blattella germanica (L.), was estimated at 14.5 micrograms/g (95% FL = 13.7-15.4 micrograms/g). Sulfluramid was significantly more toxic than topically applied hydramethylnon (LD50 = 29.2 [19.0-46.5] micrograms/g). Sulfluramid had delayed toxicity but caused mortality significantly faster than hydramethylnon after topical application. The oral LD50 against newly enclosed, fifth instars was estimated to be 4.1 (3.9-4.4) micrograms/g; this toxicity was significantly greater than when sulfluramid was topically applied. Mortality caused by sulfluramid occurred significantly more slowly in the dietary exposures than in the topical applications. Sulfluramid at 1,000 ppm in diets was not a feeding deterrent to nymphal B. germanica.