A comparison of the volume of industrial production in the United Kingdom in 1935 and 1948, using the full resources of the Census of Production, has recently been published. This provides an opportunity of testing the results obtained, much more rapidly but on more limited data, by an index of produetion. The index is shown to have underestimated the growth of production, which is in accordance with a priori expectations. The divergence between index and Census results for particular trades is frequently large; some instances are examined.