It is not known what constitutes an optimal diet in infancy. There are relatively few studies of weaning practice in the UK, and there is a need for prospective data on the effects of infant diet and nutrition on health in later life. We describe the dietary patterns, defined using principal components analysis of FFQ data, of 1434 infants aged 6 and 12 months, born between 1999 and 2003. The two most important dietary patterns identified at 6 and 12 months were very similar. The first pattern was characterised by high consumption of fruit, vegetables and home-prepared foods ('infant guidelines' pattern). The second pattern was characterised by high consumption of bread, savoury snacks, biscuits and chips ('adult foods' pattern). Dietary pattern scores were correlated at 6 and 12 months (r 0.46 'infant guidelines'; r 0.45 'adult foods'). These patterns, which reflect wide variations in weaning practice, are associated with maternal and family characteristics. A key influence on the infant diet is the quality of the maternal diet. Women who comply with dietary recommendations, and who have high intakes of fruit and vegetables, wholemeal bread and rice and pasta, are more likely to have infants who have comparable diets--with high 'infant guidelines' pattern scores. Conversely, women whose own diets are characterised by high intakes of chips, white bread, crisps and sweets are more likely to have infants who have high 'adult foods' pattern scores. The effects of these patterns on growth and development, and on long-term outcomes need to be investigated.