This paper provides a comprehensive review of scheduling problems with setup times or costs, covering over 300 papers published between 1999 and 2006. It classifies scheduling problems into those with batching and non-batching considerations, and with sequence-independent and sequence-dependent setup times. The paper also categorizes the literature according to shop environments, including single-machine, parallel machines, flow shop, no-wait flow shop, flexible flow shop, job shop, open shop, and others. The objective is to provide an extensive review of the scheduling literature on models with setup times (costs) from then to date. The paper identifies areas where independently developed techniques need to be compared. It discusses the importance and applications of scheduling models with explicit considerations of setup times (costs), including examples from various industries. The paper also provides a classification of setup time (cost) problems using a three-field notation and discusses various scheduling problems with setup times (costs) in single-machine and parallel-machine environments. The paper concludes with a discussion of the complexity of scheduling problems with setup times (costs) and the need for further research in this area.This paper provides a comprehensive review of scheduling problems with setup times or costs, covering over 300 papers published between 1999 and 2006. It classifies scheduling problems into those with batching and non-batching considerations, and with sequence-independent and sequence-dependent setup times. The paper also categorizes the literature according to shop environments, including single-machine, parallel machines, flow shop, no-wait flow shop, flexible flow shop, job shop, open shop, and others. The objective is to provide an extensive review of the scheduling literature on models with setup times (costs) from then to date. The paper identifies areas where independently developed techniques need to be compared. It discusses the importance and applications of scheduling models with explicit considerations of setup times (costs), including examples from various industries. The paper also provides a classification of setup time (cost) problems using a three-field notation and discusses various scheduling problems with setup times (costs) in single-machine and parallel-machine environments. The paper concludes with a discussion of the complexity of scheduling problems with setup times (costs) and the need for further research in this area.