Maize was grown under field conditions, applying conventional farming practices. Atrazine was sprayed pre- emergence at concentrations of 1,25 I ha−1ai. and 5 I ha−1ai. Severe phytotoxicity symptoms were visible from the first- to about the sixth-leaf stage i.e. 25–30 days after planting in the maize plants treated with 5 I ha−1atrazine. The growth rate of atrazine-treated maize plants was inhibited during this period, whereafter it recovered. No effect on subsequent fresh mass accumulation could be detected when comparing treated plants with the control after about 40–45 days after planting. The inhibition of growth during the early developmental stages had no negative effect on the final yield. Hydroxylation of atrazine as detoxifying mechanism seems to play the major role in the case of root-absorbed atrazine up to approximately 25–30 days after planting.