50 high-risk infants consecutively selected from the population of a Neonatal Follow-up Clinic were tested using both the Bayley and the Griffiths Scales on the same day by the same psychologist without prior knowledge of the medical history. The mean age at testing was 13.1 mth with a range of 12--15 mth. Scores obtained from the Griffiths Scale were consistently higher than those obtained from either of the Bayley Scales (P less than 0.001). Intercorrelations between the Griffiths and the Bayley test were high at pH 0.01. These results suggest that, although the two tests may be used interchangeably, their numerical scores are not equivalent when administered at this age.