Cercariae of Cotylurus flabelliformis (Faust, 1917) were individually tested in 6 experiments for evidence of chemoattraction to snail hosts, host-speeificity, and rate of dispersal. Five species of snails were tested: Lymnaea stagnalis appressa Say, 1821, Stagnatola eludes (Say, 1821), Physella gyrina (Say, 1821), Planorbella trivnlvis (Say, 1817), and Oxyloma retusum (Lea, 1834). The data substantiate that cercariae of C. flabelliformis have a chemo-positive attraction to undetermined diffusable substances from snails, show host-specificity, and do not attack the snail that produced them. Cercarial response time was significantly influenced by cercarial age (post-emergence), and duration of presence of snails. Newly emerged cercariae were most consistently chemo-positive to L. stagnalis and quickly located all snail species except the unnatural host O. retusum. Tests of 121 cercariae proved statistically significant in showing preferences for snail hosts. Cercarial dispersal experiments showed that C. flabelliformis cercariae can disperse rapidly but few located and penetrated lab-reared S. eludes at distances up to 1.2 m. The results are consistent with other studies which indicate that chemical gradients are used by cercariae to locate slow moving hosts and that cercariae must come into close proximity of snails before attraction occurs. The significance of these observations to the distribution of C. flabelliformis in the molluscan population is discussed.