We review recent advances in dealing with the resource-constrained project scheduling problem using an efficient depth-first branch-and-bound procedure, elaborating on the branching scheme, bounding calculations and dominance rules, and discuss the potential of using truncated branch-and-bound. We derive conclusions from the research on optimal solution procedures for the basic problem and subsequently illustrate extensions to a rich and realistic variety of related problems involving activity preemption, the use of ready times and deadlines, variable resource requirements and availabilities, generalized precedence relations, time/cost, time/resource and resource/resource trade-offs and non-regular objective functions. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.