The following conclusions are made from an introductory investigation on the use of the coccidiostat lasalocid on 11 production farms of an integrated broiler production organisation. In terms of the incidence of sub-clinical coccidiosis, no significant difference was found between the previous use of monensin and the use of lasalocid during the investigation. However, the incidence of coccidiosis decreased with the introduction of lasalocid. Despite the fact that on some farms sub-clinical coccidiosis was diagnosed, the production performance clearly improved with lasalocid. EBI figures significantly increased from 163.6 to 172.5. During the investigation, in which approximately 220,000 broilers were involved, litter quality did not differ from that of previous crops in which monensin had been used. Feathering of the broilers in the trial crops in which lasalocid was used was similar to that of previous crops.