Biometric data were collected for fully-grown and nestling Stonechats Saxicola torquata in southwest Ireland. Tarsus length, wing length and mass were collected for adult and nestling Stonechats. Mean body mass of broods increased almost linearly up to eight days after hatching when it reached an asymptote prior to fledging. Mean mass growth rates of broods declined with breeding attempts and age of broods. First broods had the highest rate of increase in body mass. The mean tarsus lengths of broods differed significantly between three sites. These observed differences were not related to age or size of broods when measured. Adult body mass declined from February, prior to the start of the breeding season, to July, which coincided with the end of the breeding season. Fully-grown birds were sexually dimorphic in wing length with males having significantly longer wings than females. © 2003 British Trust for Ornithology.