The objective of this study was to develop a parent-report psychometric measure of infant appetite during the period of exclusive milk-feeding. Constructs and items for the Baby Eating Behaviour Questionnaire (BEBQ) were derived from an existing psychometric measure validated for older ages, the Children's Eating Behaviour Questionnaire, supplemented by a review of the literature on milk-feeding behaviours. Cognitive interviewing with a sample of mothers (n=10) was used to refine the questions. The factor structure of the 18-item BEBQ was assessed in infants (one per family) from the Gemini twin birth cohort (n=2402 families). Principal Component Analysis identified four distinct appetitive constructs, all of which had good internal reliability: 'enjoyment of food' (Cronbach's α=0.81), 'food responsiveness' (α=0.79), 'slowness in eating' (α=0.76), and 'satiety responsiveness' (α=0.73). A single item assessing 'general appetite' correlated with all of the constructs. The BEBQ is the first standardised measure of infant appetite designed to characterise appetitive traits that might confer susceptibility to excess weight gain.