Artificial insemination is now widely used in the breeding of cattle and several textbooks have dealt with the subject (Hammond, Edwards, Rowson and Walton, 1947 J Perry, Bartlett, Edwards, Terrill, Berliner and Jeffrey, 1947; Rowson, Day and Griffiths, 1948; Herman and Madden, 1950; Millar and Has, 1952; Laing, 1955; Van Rensburg, 1957)» The early work on artificial insemination and on the semen of the domestic animals has been adequately reviewed by Anderson (1945). The present extent of use of artificial insemination in different countries is shown in Table 1 and this data indicates that further expansion is still possible in many countries. The arguments put forward in 1941 for its trial on a field scale were discussed in retrospect by Walton (1958) who also maintained that the economic benefit to the small farmer and that the wider use of progeny tested bulls would result in the further extension of its use in the future. The nature of the development in the different breeds in England and Wales (see Table 2) is somewhat different from what might have been anticipated; this is chiefly due to the relative decrease in the demands for insemination from bulls of dual-purpose breeds (in particular the Dairy Shorthorn) and to an increase in the demand for crossing with beef bulls. The application of artificial insemination in cattle has several advantages, The small farmer has a choice of good bulls of several breeds for less than it would cost him to keep a bull of his own (Hammond, 1953); the 'communal bull* is much leas common and it is generally agreed that the almost complete disappearance of trichomoniasis in England and Wales (Report 1958a) is due to this increased production by the use only cf proven bulla and breeding from a bull that may not be able to serve because of illness or injury or that may be too heavy for certain cows is made possible. The possible usefulness of artificial insemination for upgrading indigenous stock in underdeveloped territories has also been accepted,but it cannot always be practical under the conditions existing in mar\y of these countries. The success of artificial insemination depends very nuoh on the accurate detection of heat by the farmer (Smith, 1958). For this reason a service is of limited value where cattle arc not kept under close observation and in areas with poor means of communication.