Oleamide (1, cis-9-octadecenamide) is a naturally occurring brain constituent that. has been shown to accumulate and disappear under conditions of sleep deprivation and sleep recovery, respectively. Synthetic 1 has been found to induce sleep in a structurally specific manner at nanomolar quantities. Hydrolysis of 1 by an enzyme (oleamide hydrolase) present in the cell membrane rapidly degrades oleamide to oleic acid (cis-9-octadecenoic acid). Such observations suggest 1 may constitute a prototypical member of a class of fatty acid primary amide biological signaling molecules in which the diversity and selectivity of function are derived from the length of the alkane chain as well as the position, stereochemistry, and degree of unsaturation. A series of inhibitors of oleamide hydrolase were designed and prepared which were expected to derive their properties through interactions with the putative active site cysteine residue within oleamide hydrolase. This approach yielded a series of rapid, selective, and highly potent inhibitors (K-i = 13 mu M to 1 nM) which in addition to their potential therapeutic value may serve as useful tools to define the biological role of oleamide.