Since the hard-fought general election of February 23, 1950, the narrow margin of Labor's control of the British House of Commons has been tested at the polls on ten occasions. This number of by-elections to fill vacancies in the membership of the House is a normal post-World War II figure (the previous House saw fifty-two replacements in its four and one-half years of life), although it is somewhat under that of prewar averages. In terms of locale, however, these ten by-elections were atypical. Though the overall distribution within the various parts of the United Kingdom was not unrepresentative (six in England, one in Wales, actually Monmouthshire, two in Scotland, and one in Northern Ireland), all vacancies chanced to come in urban areas. Eight of the contests involved borough seats and the other two (West Dunbartonshire and Abertillery, Monmouthshire) were primarily urban in character.