The aligned restriction endonuclease maps of three sequenced maize streak virus isolates, three restriction-mapped southern African maize streak virus isolates, and two other sequenced geminiviruses were used as a means of calculating the sequence divergence between these viruses. The degree of divergence was used to construct a phylogenetic tree for the viruses; this tree agrees well with predictions from sequence comparisons, and so the method can be used to study the relationship of geminivirus isolates without the labor and expense of sequencing each one.