The WPPSI-R scale (Wechsler Preschool and Primary Scale of Intelligence - Revised) is a psychometric test chosen as the evaluation tool in a study on preschool-age cognitive development in a cohort of very low birth weight (VLBW) premature children from the Fernandes Figueira Institute (IFF), applied by four previously trained psychologists. The objective of this study was to verify inter-observer reliability in the test application. Two types of reliability study design were used: balanced incomplete blocks, to verify agreement in the application of the scale, and crossed design, to verify agreement in scoring of items. We studied 12 preschool children born at IFF (birthweight < 1,500g). The intraclass correlation coefficients (ICC) were: 0.82 (full-scale IQ), 0.89 (verbal IQ), and 0.91 (performance IQ), in the incomplete block design study, and 0.99, 0.98, and 0.99, respectively, in the crossed design study, indicating good reliability. Application of the WPPSI-R scale in the study of cognitive development of VLBW premature children at IFF proved adequate, as shown by these results.