Objective. To compare the cost of maternal and child health care (current model) to that of the WHO Mother-Baby Package if it were implemented. Material and Methods. A pilot cross-sectional case study was conducted in September 2001 in Sanitary District No. III, Morelos State, Mexico. Two rural health centers, an urban health center, and a general hospital, all managed by the Ministry of Health, were selected for the study. The Mother-Baby Package Costing Spreadsheet was used to estimate the total cost and cost per intervention for the current model and for the Mother-Baby Package model. Results. The total cost of the Mother-Baby Package was twice the cost of the current model. Of the 18 interventions evaluated, the highest proportion of total costs corresponded to antenatal care and normal delivery. Personnel costs represented more than half of the total costs. Conclusions. The Mother-Baby Package Costing Spreadsheet is a practical tool to estimate and compare costs and is useful to guide the distribution of financial resources allocated to maternal and child healthcare. However, this model has limited application unless it is adapted to the structure of each healthcare system.