A two-part study was conducted in several centres in Nigeria to develop and evaluate a simple method for maturity determination in newborn infants. The first part involved the development of a six-feature model which included head circumference, mid-arm circumference, skin texture, ear form, breast size and genitalia. These were features which had highly significant correlation with gestational age in the studied population. The model consisted of a chart showing the regression line of gestational age on total maturity score based on the six selected features. It had comparable accuracy with the Dubowitz method. Different subgroups of term and low-birth weight infants were also reliably identified by the model. In the evaluation of sick newborn infants, the model was more accurate than a previously reported abbreviated method from the same population. The model is suggested as an appropriate clinical tool for rapid and reliable maturity determination in healthy and sick newborn infants.