The distribution in Britain of carrion-attracted Calliphorinae was examined by simultaneous trappings, under standard conditions, at 51 stations so distributed as to be more or less representative of the country.

From published records and other sources, the known distribution of each species by vice-counties was delimited and compared with the observed results.

Lucilia sericata (Mg.), L. caesar (L.), Calliphora erythrocephala (Mg.) and C. vomitoria (L.) are generally distributed. L. illustris (Mg.) is more widely distributed than was recognised, and is probably general, though relatively uncommon in hill country. Phormia terraenovae R.-D. and Cynomyia, mortuorum (L.) are also general, though more common in the north. The decrease in frequency southwards is more pronounced with C. mortuorum. and both species occur only rarely in Wales. L. silvarum (Mg.), believed previously to be confined to England, is also possibly generally distributed; it was trapped as far north as Caithness. It is uncommon north of the Highland Line.

Lucilia ampullacea Villen., for which known records are restricted to south of the Humber-Mersey line, appears similarly to be almost general; it was taken both in hill and plains country up to the Inverness region.

Of the remaining species that show some degree of geographical limitation, Acrophaga subalpina (Ringdahl) is the most widely distributed. It occurs at least as far north as the Inverness region, and south to the Severn-Wash line.

The only Lucilia species with clearly restricted distribution is L. richardsi Collin. Its known territory was England south of the Pennines; this has now been extended into Wales and north to Cumberland and Durham, with one isolated record for the north-east of Scotland.

Calliphora loewi End., believed a northern species, was taken throughout Scotland and northern England. C. uralensis Villen. is restricted to the northwest, and the Western Isles.

Brief notes are given of the habitat preferences and seasonal distribution of the species.