The ceroid pigment of macrophages were subdivided into four different types according to their own color and their ability to stain with luxol fast blue. With reference to this mode a series of more than 200 brain infarcts which had happened 1 day to 56 years before death, was examined systematically. According to the results the ceroid variants do not only succeed one another chronologically but they also represent histochemically successive phases of development which correspond to the progressive auto-oxidation of unsaturated lipids. The occurrence of the different stages is chronologically defined. During this development cortical and subcortical macrophages show different speeds in the ageing process of their pigments. There is no evidence for an essential participation of proteins in the maturation of the ceroid. Not during any phase of development is the reaction pattern identical with that of neuronal and glial lipofuscin.