Efficacy of insecticides against many species of wireworms is often measured by indirect observations of associated wireworm damage (i.e. stand, yield and/or cosmetic damage) to various crops. This paper examines the effects of various classes of insecticides on a major wireworm pest, Agriotes obscurus, using direct toxicological criteria in laboratory bioassays, and direct and indirect criteria in field trials involving wheat and potatoes. The long term intoxication and subsequent recovery of wireworms exposed to various neonicotinoid insecticides is the focal point of this paper.