The following paper presents the methodology and results of a costing exercise of maternal health services in Tanzania. The main objective of this study was to determine the actual costs of antenatal and obstetric care in different health institutions in a district in Tanzania as a basis of more efficient resource allocation. A costing tool was developed that allows the calculation of costs of service units, such as deliveries and antenatal care, and separates these costs from the costs of other services. Time consumed by each activity was used as an allocation key. For that purpose, we recorded the personnel consumption with different time-study methodologies. This approach was tested and implemented in Mtwara Urban District, South Tanzania. The results were analyzed by a spreadsheet program. The paper presents average costs for different costing units of maternal care. Among other findings, we found that the cost of a normal vaginal delivery is US $12.30 in a dispensary and US $6.30 in the hospital--a result that needs explanation, as usually one would expect that hospitals are more cost-intensive than first-line facilities. However, dispensaries are grossly underutilized so that the costs per service unit are rather high. The cost for surgical delivery (only in hospitals) was found to be US $69.26 and the average cost per antenatal care consultation (only at dispensaries) was US $2.50. We conclude that improved planning of elective services is a prerequisite for more effective and efficient use of personnel resources. In addition, the definition of medically and economically sound standards, in particular staffing standards, is critical to make cost analysis an effective management tool to guide rational resource allocation.