Recently, maize (Zea mays L.) genetic maps based primarily upon segregating restriction fragment length polymorphisms (RFLPs) have been developed by several research groups. Some of the reported maps were based upon data from a single segregating population, whereas others were based upon information from several segregating populations. Potential problems with pooling information from several segregating populations have not been reported. These include the fact that few genetic markers are polymorphic in all populations, estimates of linkage may differ among populations, and population sizes may differ. We utilize the log-likelihood statistic to genetically map partially overlapping sets of informative genetic markers, to test homogeneity of recombination among populations, and to present a composite RFLP linkage map based upon data pooled from four F2 populations.