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We consider the problem of minimizing the makespan of n jobs in an m-machine flowshop operating without buffers. Since there is no intermediate storage, a job here cannot leave a machine until the machine downstream is free. When that is the case, the job is said to be blocked. This “blocking flowshop” problem is known to be strongly NP-hard for the shop having more than two machines. In this paper, we develop a genetic algorithmic approach to solve large size restricted slowdown flowshop problems of which blocking flowshop problems are a special case. Abadi (Flowshop scheduling problems with no-wait and blocking environments: A mathematical programming approach. Ph.D Thesis, Department of Industrial Engineering, University of Toronto, Canada, 1995) has established a connection between the blocking flowshop problem and a no-wait flowshop in which jobs do not wait between operations. He …