Pilot trials are described in which BHS, a Czechoslovak fasciolicide, was employed for mass treatment of fasciolosis in cloven-hoofed animals in wild-animals' reserves at the rate of 30 mg body weight using BHS-medicated feed. The treatment was combined with control measures against the intermediate host snail, Lymnaea truncatula, in primary biotopes using Frescon, a molluscicide of English origin, and CF-4, a molluscicide of Czechoslovak origin, at concentration of 1 and 0.5 per cent, respectively. Where the application of molluscicides was impracticable the intermediate host snails were controlled by means of sciomyzid larvae or by blasting surface layers of the soil.--Using this combined approach, the extensity of infestation, evaluated on the basis of coproovoscopical examination, was reduced from 7.05 to 0.71 per cent. The extensity of infestation, evaluated on the basis of necropsy findings, was reduced from 50 to 6.2 per cent. The intensity of infestation was reduced from 7.7 to 0.31 per cent per animal.--The results may prove useful in devising fasciolosis control schemes based on a complex approach.