During 1963, pigs tested at the five pig progeny testing stations in Britain were examined and scored by each station manager for leg weakness at the end of test. Some 19 individual items were scored, the score being 0 if satisfactory, 1 if a mild fault and 2 if a serious fault. In addition an overall legs and action score was given, scoring on a scale from 1 to 6 points; in this case the higher the score the better the leg condition. Data were available on 1,240 Landrace and 1,892 Large White pigs (2 females and 2 castrated males per litter)from 128 and 202 sires respectively. Sex differences in incidence were small,most of them being less than a tenth of a standard deviation unit, and so the analyses were performed ignoring sex. To avoid any effects of differences in incidence and in scoring among stations and to avoid the effects of any trends in the scoring pattern over the year, the analyses were performed within three-monthly periods within stations.