In the light of a still prevalent view that health inequalities are an invariant feature of the life-course, this paper re-examines the thesis that youth, in contrast to childhood, is characterised by relative equality in health, and proposes a process of equalisation to account for changes in the social class patterning of certain dimensions of health between these life stages. The evidence relating to the relationship between class of background and health over the early years is first reviewed, focusing on seven dimensions of health: mortality, chronic illness, specific conditions, self-rated health, symptoms of acute illness, accidents and injuries, and mental health. The overall picture is consistent with a conclusion of relative equality of health in youth with one major exception, severe chronic illness, which particularly on the evidence of the 1991 British Census is class differentiated from infancy. In respect of other dimensions of health, notably symptoms, non-fatal accidents and (probably) mental health, there is evidence of a change in class patterning between childhood and youth consistent with a hypothesis of equalisation. Within a theoretical perspective that juxtaposes class and age (youth) based influences, it is suggested that this could occur when effects associated with the secondary (high) school, the peer group and youth culture cut across those of the family, home background and neighbourhood in such a way as to reduce or remove class differences in health. In later youth, in the post-school period, the relative balance of class and age based shifts once more to produce a "re-emergence" of class gradients in adulthood. Youth may be a barometer of the relative power of post-modern consumer culture and traditional class based structures to shape the pattern of health inequalities over the early years into adulthood.