The effect of ethnic origin on respiratory function was assessed in 57 young children aged between 4.9 and 8 years. Functional residual capacity (FRC) and peak expiratory flow rate (PEFR) were measured and related to sitting and standing height in Caucasian and Afro-Caribbean children. No significant differences were found between the two groups in PEFR when related to either standing or sitting height. FRC, when related to standing but not sitting height, was greater in Caucasian children (P less than 0.01). Sitting height related to standing height was lower in children of Afro-Caribbean descent (P less than 0.01), suggesting that anthromorphic differences may explain the apparent influence of ethnic origin on respiratory function in young children.