Abstract: All trials were conducted in 2000, 2001 and 2002 with different canola (Brassica napus L.) and mustard (Brassica juncea (L.) plants to evaluate the relative host plant preferences of Western Black Flea Beetle (WBFB) Phyllotreta pusilla Horn (Coleoptera: Chrysomelidae) in greenhouse and field conditions in Colorado (USA). The spring mustard (ZEM1) and winter mustard (Debut) were significantly attractive and more susceptible for the WBFB. However, the spring mustard (W1-23) was less susceptibility to WBFB and suggests a possible source of reduced susceptibility in oilseed mustards. Most of currently registered varieties of canola were susceptible to WBFB feeding. The spring canola (CO1) was significantly more attractive and susceptible for the WBFB. In addition, spring canola (Helios) sustained relatively high plant injury with WBFB and plant had low population density and suggesting in tolerance to WBFB injury.