The influence of prenatal exposure to aluminium sulphate (Al₂(SO₄)₃) on the behavioural development of mice (Mus musculus) from two inbred strains was examined. Pregnant CBA/T6 and C57BL/6J mice were exposed by intraperitoneal (i.p.) injection (200mg/kg) or orally (750, 1000 and 1250mg/L) to Al₂(SO₄)₃. On postnatal day one, pups were cross-fostered and tested in a variety of ethological measures, from birth to adulthood, to assess effects on the mother and the behavioural development of the pups. As a neurochemical marker for the cholinergic system, choline acetyltransferase (ChAT) activity was measured at different developmental stages. Breeding performance, the length of gestation and sex ratio were unaffected by Al exposure administered via the i.p. route. There was a transient reduction in maternal weight gain during gestation. CBA pups born to Al-treated mothers exhibited lower body weights at birth; this reduction persisted into adulthood only in treated pups reared by treated mothers and was more pronounced in the case of female mice. The body weight changes were accompanied by delays in the maturation of several of the tests of sensory-motor development. Al-treated CBA females were hypoactive at weaning compared to controls, whilst the converse was true for males. 77% control and 55% treated males reached criterion in a maze test and controls required fewer days to do so. The effect of Al exposure on the cholinergic system was dependent on the region of the brain studied, and still showed significant effects in the adult. In utero exposure to injected Al resulted in a reduction in the rate of ultrasonic calling by CBA pups and was accompanied by a delay in the timing of peak calling. C57 pups were not affected to the same degree. Exposure to oral Al caused a similar but less obvious trend towards a diminished calling. The inclusion of the recording of ultrasonic calling is recommended in any test battery aimed at assessing behavioural teratogenicity.