A removal programme, specially designed for catteries or multiple cat households, to reduce the incidence of lymphosarcoma or leukaemia in cats and the spread of feline leukaemia virus (FeLV), is discussed. This removal programme includes annual testing of male stud cats, testing all contacts of FeLV-positive cats they had during the past two years, testing cats imported from abroad and isolation--or, if this is not possible, euthanasia--of cats found to be positive for FeLV-antigen. To detect the FeLV-antigen a simple indirect fluorescent antibody technique (FAT) was used to detect FeLV-antigen. During a period of four years, the following results were obtained when a removal programme was carried out by a large cat breeders' association in the Netherlands. The proportion of catteries, in which FeLV-positive cats were found to be present, decreased from 11.5 per cent in the former half of 1974 to 2.1 per cent in the latter half of 1977. The proportion of FeLV-positive cats and male studs decreased from 4.9 per cent to 1.2 per cent and from 5.9 per cent to 1.0 per cent respectively during this period. It is concluded that the recommended removal programme is a simple and successful procedure.