Infant rabbits received s.c.injections 3 times weekly of low doses of aluminium (A1) maltolate (0.5-1.5 mg Al/kg body wt) or aluminium lactate (8 mg Al/kg body wt) from 5 or 10 days of age to 14 or 22 days of age. 2. Brain was used to provide a cell-free protein synthesizing system and this system exhibited increased activity in preparations from Al-exposed infants. The mRNA fraction obtained from the brain polysomal RNA also was more active following Al exposure. 3. The synthesis of immunoprecipitable calmodulin was significantly elevated.