In response to a request from the IWC Scientific Committee, this paper investigates the disagreement between two sets of Japanese statistics for the Dall’s porpoise fishery, with particular reference to the Iwate Prefecture where most of the catches were landed. The earlier statistics, compiled by the Far Seas Division of the Fisheries Agency, were based on reports from fishery cooperative unions (FCUs), and covered the years 1972-1987. They underestimated the catch, at least in recent years, due to incomplete prefectural coverage and the inability of some FCUs to obtain access to the records of some fish markets. Another series started in 1986 by the Coastal Division was based on reports from the Iwate Prefecture Government using landing records in fish markets. For the available years (1987 and 1988), the latter statistics gave values LS to 1.8 times greater and seemed to be closer to the true catch, but they still contained errors due to incorrect conversion factors in convening weight into animals. manipulation by some FCUs to increase the numbers of licensees, and omissions due to selling through fish markets outside the prefecture of registration. The sum of these effects is difficult to assess, but may result in underestimates of 10% or more. The prefectural staff believe that the above mentioned deficits have been improved since 1989. I was not in a position to verify this in the present study. Further effort is needed to include catches sold through markets outside the prefecture and those sold direct to dealers, and to improve the identification of porpoises and dolphins by species and stocks.