SNAREs mediate the specificity of membrane fusion in eukaryotic cells. Using a yeast 2-hybrid screen with Drosophila a-SNAP as bait, a Drosophila cDNA library was screened to identify syntaxin 1, 5, 16, and SNAP-29. At the time of these findings, syntaxin 16 and SNAP-29 had not previously been discovered in any organism, while syntaxin 5 was uncharacterized in Drosophila. This book describes the characterization of these proteins. Exploiting a combination of genetics, biochemistry and fluorescence microscopy, the author and his colleagues show that dSyx5 and dSyx16 are required for the proper function of the Golgi apparatus and that an efficiently functioning Golgi apparatus is required for the steps leading to the completion of cytokinesis and formation of mature sperm. In contrast, Drosophila SNAP-29 (dSNAP-29) is localized to both the plasma membrane and cytoplasm, but its intracellular distribution pattern does not match that of the ER, Golgi, early endosomes, late endosomes, or lysosomes. Inhibition of SNAP-29 function or expression in Drosophila leads to lethality, suggesting an essential role for SNAP-29 mediated membrane traffic.