Fischer 344 rats and B(sub 6)C(sub 3)F(sub 1) mice were divided into groups and treated. The 'in-life' part of this study was conducted at Bio/dynamics (Project Number 89-819-1: A=Rats, B=Mice). Duplicate sections from each kidney specimen (high and control animals) were prepared and mounted at Bio/dynamics. The first series was processed to hematoxylin and eosin stained slides at Bio/dynamics. All hemotoxylin and eosin and unstained kidney slides were sent to Experimental Pathology Laboratories (EPL) where a second series was stained with Mallory Heidenhain stain according to the attached procedure. The purpose of this study was to evaluate hydrocarbon induced kidney changes by grading hyaline droplet change, regenerative epithelium and by estimating tubular dilatation with granular material as per the attached criteria. All slides were evaluated coded or in a 'blind' manner, the computer assigning random numbers to the slides for each animal regardless of treatment group. The slides were then examined 'blind' and the renal lesions dictated. The Pathology Support Groups at EPL entered the diagnoses into the computer which then decoded the results, issuing Histopathology Incidence and Summary Tables.