In many realistic situations, a job processed later consumes more time than the same job when it is processed earlier; this phenomenon is known as deteriorating jobs. However, job deterioration is relatively unexplored in the context of group technology. In this paper, we consider deterioration in the framework of minimizing the makespan and the total completion time in single-machine group scheduling problems. We show that these problems remain polynomially solvable when deterioration is considered. 2006 Elsevier Ltd. All rights reserved.