Two cohort studies conducted in Ribeirão Preto (RP), SP and São Luís (SL), MA, performed a complete assessment of the participating children both at birth (1994 in RP and 1997 in SL) and at school age, with the inclusion of psychological evaluation at the second time point. The wealth of data obtained permitted the study of the association between birth conditions and psychological development at school age. Particularly interesting among the aspects investigated were the presence of prolonged non-nutritive sucking habits and the occurrence of emotional and behavioral problems. Birth data were collected using standardized questionnaires applied to the puerperae soon after delivery, measurement of anthropometric parameters of the newborns, and demographic and socioeconomic information. The data collected again in RP and SL at school age referred to PNNSH, considered to be prolonged when they lasted 36 months or more, and to nutritive sucking habits (use of a bottle, sleeping with a bottle, breast-feeding), and to psychological tests for the evaluation of affective and behavioral performance based on the application of the Strengths and Difficulties Questionnaire (SDQ).