The navel orangeworm, Paramyelois transitella (Walker), is a sporadic pest of almonds in California. Crop damage caused by this pest tends to increase and persist at an economically significant level for a few years in a particular locality, and then to drop to a low, chronic level for an indefinite period. The factors causing these changes in infestation are not known. Since this moth does not attack an almond crop until the nuts begin to ripen, the grower usually does not appreciate the extent of its damage until harvesting begins. A system to detect and assess changes in the pest population would enable growers to adjust harvest operations, if necessary, to minimize damage; for example, to harvest and fumigate susceptible soft-shell varieties as early as possible. These studies were to determine the value of chemical attractants in a detection program.