A serological survey carried out on 1379 school-children from Skye and Mallaig in the N.W. of Scotland failed to show evidence of subclinical cases of hydatidosis. There appeared to be a relatively low level of exposure to the parasite, as judged by ELISA and IHA tests. Thirty-one children reacted positively in the ELISA; only one child had a transient positive result in the IHA test. Surveillance of these children will be continued for the present but the duration required is uncertain. The local population appeared to be well aware of the mode of spread of the parasite and the methods for its control.