Thirty-three maize (ZeamaysL.) inbreds were screened for tolerance to atrazine (2-chloro-4-ethylamino-6- isopropylamino-1,3,5-triazine) in a glasshouse using a sand culture technique. Tolerance ranged from 95,7–51,0% of the control. The continuous pattern of tolerance exhibited by the inbreds indicated polygenic inheritance. Six inbreds categorized as either highly tolerant or less tolerant were hybridized in all possible combinations. The six inbreds and Fl crosses were evaluated for tolerance to atrazine (6 p.p.m. v/v) under controlled conditions. Leaf mass data strongly suggested additive gene effects. Broad-sense heritability (0,66) indicated the potential for increasing hybrid tolerance to atrazine by breeding. The nature of gene action could not be established when veinal chlorosis was used as a measure of atrazine toxicity.S. Afr. J. Plant Soil1986, 3: 27–30