The influence of tillage system and imidacloprid seed treatment on flea beetle (PhylJotreta cruciferae (Goeze)) damage, oilseed production, volunteer barley density, and post harvest residue cover was determined for Polish canola (Brassica rapa L.) and yellow mustard (Sinapis alba L.). Field trials were conducted at Moccasin, MT, USA, from 1998 through 2000. Flea beetle damage was assessed on cotyledon and first true leaf stage plants using a numerical damage rating. Flea beetle damage was low in both tillage systems and on both plant species when imidacloprid seed treatment was applied. In the absence of seed treatment, seedlings of both plant species in conventionally tilled plots usually suffered more damage than did seedlings in zero tillage plots. Canola often sustained more damage than yellow mustard. Across tillage system and insecticidal seed treatment, yellow mustard produced significantly greater (P > 0.01) seed yields than canola. Density of volunteer barley was significantly greater (P > 0.01) in conventionally tilled plots. Postharvest residue cover was greater in zero-tillage plots, but all systems easily met USDA, Natural Resource Conservation Service specifications designed to prevent soil erosion.