Statistical process control procedures typically entail monitoring the process by selecting rational subgroups of equal size at equal time intervals. A generalization of this standard paradigm removes the restriction of equal waiting times between subgroups. We consider process control procedures where the time until the next subgroup is shortened when there is evidence that the process is off target, with a compensating lengthening of the waiting time otherwise. This adapting of the waiting time significantly improves the performance of the process control procedure. Using the ShewhartX̄procedure as an example, the adaptive sampling strategy is introduced. A simple, dual waiting time procedure is described and shown to be optimal and easy to implement in practice. Performance comparisons to classical procedures are provided.