A 14-day repeared dose range finding toxicity study was conducted with rats to derermine dose levels for a subsequent 91-day study with the test article, AK 3039. The rest chemical was incorporated into the diet of rats at concentrations of 0 (Control), 10, 100, 500, 1000 and 5000 PPM. The rest chemical at dose levels used in this study had no effect on body weight, feed consumption, blood biochemical parameters, urinalysis or organ weights. Gross examination on necropsy revealed speckled renal tissue at dose levels of 500, 1000 and 5000 PPM. Microscopic examination of kidneys revealed mild easinophilic granular degeneration of proximal rubules at 500 PPM which progressed to proximal tubule nephrosis associated with faintly cosinophilic 'crystalline' deposits at higher dose levels. Results of this study suggest that the 10 and 100 PPM levels are 'no-effect' levels whereas the 500, 1000 and 5000 PPM dose levels are 'effect' levels based on gross and microscopic renal pathology.