Thecis‐ and trans‐decalin stereoisomers have found many uses as solvents and fuel components. The metabolism of the decalin isomers in male and female Fischer‐344 rats and the effects of the decalins on renal damage were evaluated. Only male rats had kidney damage. Metabolism of cis‐decalin yieldedcis,trans‐7‐decalol andcis, cis‐2‐decalol in the urine of both sexes, with the male also producing cis,cis‐1‐decalol. The urinary metabolites of trans‐decalin included trans, cis‐2‐decalol in both male and female rats andtrans,trans‐7‐decalol in males. Extracts of kidney homogenates from male rats, but not from females, dosed with cis‐ and trans‐decalin yieldedcis‐2‐deca‐lone andtrans‐2‐decalone, respectively. A single male rat treated with trans‐decalin produced no 2‐decalone in the kidney extract and also showed no renal damage.