The giant African snail, Achatina fulica, followed trails made with the mucus of A. fulica, but did not follow those consisting of mucus from Otala vermiculata. In olfactometer experiments, A. fulica and Helix aperta oriented preferentially toward the odor of their own species when both odors were presented simultaneously. Species specificity was less pronounced when the odor of O. vermiculata was paired with either of the other two snail odors. Sexually mature A. fulica that had been housed individually for 30 days prior to testing followed mucus trails better than did similar snails housed collectively. Immature A. fulica did not follow trails better after isolation, but showed a facilitative effect of isolation on conspecific orientation in the olfactometer. Three-week-old snails, maintained in individual containers from the time of hatching, also oriented preferentially toward conspecific odors. © 1978 Academic Press, Inc.