The functions of most Drosophila odorant binding proteins (Obps) remain unexplored, and many exist in tandem arrays throughout the genome. As these genes most likely arose through recent duplication, genes within a cluster likely have partially redundant or pleiotropic functions. Here, we used the CRISPR-Cas9 system to generate two knock-out lines, the first lacking the four paralogs of the Obp56a-d cluster, and the second lacking the single Obp56h gene, another possible paralog of the Obp56 cluster. Various phenotypic tests on these knockout lines demonstrate significant functional overlap and novel pleiotropic functions. Both lines shared decreased viability in early development and development time, while the Obp56a-d KO line uniquely showed decreased height of pupation. The Obp56h KO line showed increased copulation duration and decreased aversion to 2-heptanone. Reinserting the Obp56a-d genes one-by-one and in various combinations in a PhiC31 integration site engineered in their original location during CRISPR-Cas9 excision will enable reconstruction of their functional evolutionary history. Supported by NIH grant GM059469.