\input zb-basic \input zb-ioport \iteman{io-port 01339944} \itemau{Kimms, A.} \itemti{A genetic algorithm for multi-level, multi-machine lot sizing and scheduling.} \itemso{Comput. Oper. Res. 26, No.8, 829-848 (1999).} \itemab Summary: This contribution introduces a mixed-integer programming formulation for the multi-level, multi-machine proportional lot sizing and scheduling problem. It also presents a genetic algorithm to solve that problem. The efficiency of that algorithm is due to an encoding of solutions which uses a two-dimensional matrix representation with non-binary entries rather than a simple bitstring. A computational study reveals that the proposed procedure works amazingly fast and competes with a tabu search approach that has recently been published. \itemrv{~} \itemcc{} \itemut{multi-level lot sizing; scheduling; genetic algorithms; PLSP} \itemli{doi:10.1016/S0305-0548(98)00089-6} \end