Surface active agents of various kinds are widely used in the wet processing of wool at many stages. The final product may also be subjected to many domestic launderings during its life in non-ionic or anionic detergents; cationic surfactants are present in the softening agents sometimes added in the last rinse. It is well known that surface active agents are sorbed by wool and a considerable amount of work has been published on this subject, but until fairly recently there has been little or no published work on the effect of their presence in wool on its chemical reactivity under various conditions, apart from the early work by Steinhardt et alia on acid hydrolysis (9). However, in 1970 and 1971 work was published in Spain and in Germany dealing with variouss aspects of this problem. There is some contradiction between the results from these two sources, which emphasises the need for more work. It is hoped that publication of this article will draw the attention of the other research workers to these investigations, which seem to be less well known than they deserve to be. The use of wetting agents to reduce acid damage in carbonising will not be dealt with here, because of lack of space and because different phenomena seem to be at work. However, it should be mentioned that some recent work on carbonising in the presence of surface active agents has shown that under certain operating conditions the addition of an anionic surface active agent may increase acid damage in carbonising rather than reduce damage.