The effect of 8 tensides on the toxicity of diazinon were investigated by means of topical dose applications to male adult German cockroaches, Blattella germanica (L.). Other diazinon formulations were evaluated for comparison. These were Diazinon 4E, Diazinon 4E plus Igepal CO-630, Oiazinon 4E plus Multi-Film X-77, diazinon in OMSO, diazinon in Stoddard's Solvent, and diazinon in Stoddard's Solvent plus piperonyl butoxide. Five of the tensides formed emulsions that were similar in toxicity to diazinon in Stoddard's Solvent. These were, in order of decreasing L050 's, Bio Film, Tween 80, hexadecyltrimethyl ammonium bromide (HAB), Multi-Film X-77, and Triton X-100. All of the tenside emulsions were more effective than Oiazinon 4E. Emulsions formed with Triton X-100 and Multi-Film X-77 had L050 's significantly lower than the Oiazinon 4E formulation. The two tensides added to Oiazinon 4E seemed to decrease effectiveness. OMSO and piperonyl butoxide were the two most effective additives to diazinon. Both were synergistic with respect to diazinon in Stoddard's Solvent. The results from this investigation indicate that several of the tested formulations may prove effective in cockroach control. Additional studies of these preparations under practical conditions need to be made. / Master of Science