Gibberellin-deficient dwarf1 maize mutant seedlings are at least ten times more sensitive to EPTC (S-ethyl-N,N-dipropylthiocarbamate) phytotoxicity than normal maize. Levels of reduced glutathione and the enzymes cytosolic and microsomal glutathione S-transferase (important in the detoxication of the herbicide) are not significantly different in dwarf and normal maize. Our data suggest that EPTC phytotoxicity is related to alterations in gibberellin metabolism in maize plants.