The frass of virgin female Scolytus multistriatus (Marsham) evokes an excitant-turning reaction from walking male beetles in a laboratory olfactometer; frass from virgin males or mated beetles is relatively inactive. Walking virgin-female beetles are less responsive than males to virgin-female frass. Fragments of host material in the frass probably contribute to its stimulatory activity, especially in frass from males or mated beetles, but it is only partly responsible for the activity of virgin-female frass. We believe a pheromone contained in or on the fecal pellets is responsible for most of the activity of virgin-female frass. A pentane extract of virgin-female frass elicits the same response from male beetles as an equivalent amount of frass.