Seventeen analogs of the repellent compounds N,N-diethyl-3-methylbenzamide (DEET) and N,N-diethylphenylacetamide (DEPA) were evaluated in vitro for repellency against laboratory-reared Aedes aegypti (L.) and Anopheles stephensi Liston mosquitoes by using a modified membrane blood feeding test system. The system was a valuable tool for comparing the effective concentrations of the repellent analogs. Additionally, this method used easily controlled test conditions, allowing completion of the many test replications necessary to evaluate all of the repellent analogs over a period of several years. One compound, N,N-diethyl-2-[3-(triflouromethyl)phenyl]acetamide, provided significantly better repellency than DEET against Ae. aegypti and slightly improved efficacy against An. stephensi. Eight of the analogs were as effective as or slightly more repellent than DEET against both species. Seven analogs were less effective than DEET and one compound, N,N-diethyl-3-hydroxybenzamide, was as a poor repellent. Overall, two DEPA analogs and a single DEET analog provided better repellency than DEET against both mosquito species and warrant future laboratory and field evaluation.