During embryonic development, the somatic gonad precursors become populated by the primordial germ cells. While many genes have been identified, the highly regulated process of germ cell migration across the primordial midgut epithelium is not well characterized. Here, we describe three spot (tspt), a gene which interacts with tre1 during cross-epithelial migration. The tspt mutant was created in an EMS mutagenesis screen performed previously. Embryos from tspt mothers appear to exhibit restricted germ cell migration through the posterior midgut, resulting in a population of germ cells that remain associated with the endoderm through stage 16. We show that tspt is a maternally required migration gene, as well as a temperature sensitive mutant. We have identified two deletion regions that fail to complement tspt. One of the regions maps to the same region defined by recombination mapping. P-element insertions for 19 genes in and around this region were tested for germ cell phenotypes. Surprisingly, three of the nineteen exhibited germ cell defects. The Tre1 G-protein coupled receptor gene has been shown to be necessary for both programmed cell death and the migration of germ cells across the midgut. The scattershot allele of tre1 fails to complement tspt mutants, suggesting that they may be involved in the same or converging pathways during germ cell migration. Here we will describe the characterization of tspt mutants and the mapping of the tspt gene.