Modern colorants use a variety of chromophoric groups which in turn, may carry a wide range of substituents, both to influence the color, and to provide the required properties for dyeing particular substrates. Thus, there are many thousands of different substances used as commercial colorants. Further, the introduction of new structures to meet particular demands for shade and application is still in an area of major innovative activity. However, in general, individual products have a relatively low sales volume and the strategy which has been developed to assess the effect of dyestuffs (water-soluble, or water-dispersible, colorants) in the environment must necessarily be different from that appropriate for, say, pesticides. The paper discusses this strategy and shows how a "base set" package of data, the concept of which was developed by the colorant industry some years ahead of the "6th Amendment" Directive, may be used to assess the possible effects of a specific dyestuff when discharged in an aqueous effluent. As a second part of the strategy, the paper addresses more general questions relating to the ultimate fate of dyestuffs when discharged in aqueous effluents and in particular considers their most likely environmental distribution, their potential for bioaccumulation, and their biodegradability.