T HE Bureau of Labor Statistics since I927 has published a breakdown to indicate the number of work stoppages and the workers involved in jurisdictional disputes.' It is the conclusion of this note that these statistics are completely unreliable as a measure of the absolute number of jurisdictional disputes or as an indicator of their variation over time. Unless methods of reporting can be improved,2 the breakdown on jurisdictional disputes in the B.L.S. statistics should be discontinued. It is possible to compare the B.L.S. figures with the records of the National Joint Board for Settlement of Jurisdictional Disputes in the Building and Construction Industry. This private machinery, created by agreement between major contractors' associations and the unions, became effective May i, I948.3 The comparison is particularly significant since by common consent the vast majority of all jurisdictional work stoppages take place in the building and construction industry. Before presenting the figures, it must be noted that the B.L.S. data have a more comprehensive scope by virtue of the following factors: (a) The private machinery does not handle disputes, even in the construction industry, with unions outside the A.F.L. Building and Construction Department. This exclusion for practical purposes would apply to those disputes with the machinists and to disputes with industrial unions over the borderline between maintenance and construction work. (b) Not all jurisdictional work stoppages within the province of the private machinery were presented to it for settlement, although any contractor hiring union men could present a request for a decision on agreeing to be bound by the ruling of the private machinery. There is no way to estimate the proportion of all jurisdictional work stoppages in the industry presented to the Joint Board; the fraction is no doubt very large. Table i indicates the number of jurisdictional work stoppages reported by the B.L.S. and those presented to the Joint Board in the building and construction industry since May i, I948.4 The figures from the private machinery show separately work stoppages in which one or more unions were on strike from instances in which the contractors shut down the disputed work or the whole project as a consequence of a threat of strike.