Three types of international recommendations are necessary on CATs (chromatic adaptation transforms). CAT-Type I and CA T-Type II are for general use on chromatic adaptation studies. The former is related to chromatic adaptation theory and the latter to performance on field trial data. In addition, CAT-Type III is necessary for a specific and practical purposes. The need for classifying to CAT-Type I and CAT-Type III is found from a careful inspection of the development process from Nayatani et al. transform to BFD transform, referring to the Ph. D. thesis by Lam (University of Bradford, 1985). The process clearly shows two types of flows on the development of various CATs. One is the flow for deepening the theory of chromatic adaptation (CAT-Type I), and the other is for giving good performance to existing field trial data and also ease of use (CAT-Type II). Additional CAT-Type III is, for example, CAT recommended in CIE TC 8-04 technical report. The CAT is only applicable to compare hardcopy and softcopy images for the specified observing conditions in the report. Still, a difficult problem, determination of corresponding colors, remains in the method of subjective estimation, which is useful and widely used for estimating chromatic adaptation effects experimentally. (C) 2006 Wiley Periodicals, Inc.