Cytotoxic effects of aluminium sulphate on root-tip cells of Allium sativum during a time-course study and during recovery were observed. The endpoints considered were mitotic index and frequencies of aberrant cells and micronuclei induced. Chronic exposure induced mitotic depression and abnormal cells to a degree directly proportional to the concentration used and the period of treatment up to 24 h. A reduction of the early higher level of toxicity was noticed following 48 h of treatment and subsequent recovery in aluminium-free nutrient media in experiments carried out with lower concentrations. © 1989.