Drosophila Ecp is a phylogenetically conserved protein with homologs in most eukaryotes. Studies on Ecp homologs in rat and human suggest those proteins might be involved in cell cycle control, cell proliferation, and learning and memory. However, the molecular function of Ecp itself remains unclear. We show that both the mRNA and protein of ecp are ubiquitously expressed during the entire fly embryogenesis and life cycle. Results of co-immunoprecipitation show that Ecp forms a stable complex with many ribosomal proteins, including dRPL5. The binding of Ecp to dRPL5 was confirmed by GST pulldown. Furthermore, Ecp was found to cosediment with ribosome subunits in a sucrose gradient. These results indicate that Ecp might be a novel ribosome associated protein interacting with dRPL5.