This paper examines a scheduling method to improve productivity in resource-constrained projects. When resources are nonrenewable the duration of each activity has only one value. Optimal solutions are derived through criticalism of groups of activities using the same resource so as to eliminate interruption times and associated costs. The corresponding resource histogram is balanced and its design is derived by means of a program suitable for personal computer implementation. In the case where resources are renewable, activity durations are resource driven. We introduce a new view of discreetness for activity execution times which enables us to obtain optimal solutions relating to the cost functions of the activities. Finally we account for doubly constrained resources by (a) defining a maximum level of resource utilization and a maximum cost increase per period of usage of renewable resources and (b) considering as acceptable only those optimal solutions which keep total cost increase for the overall project below a tolerable limit. An application example is given using personal computer and commercially available software.