Thomas McKeown was right in his primary claim that changing environments, rather than improved medical care, were responsible for much of the long wave of historical mortality decline in the UK since 1700. He was, however, apparently unaware that the beginning of the decline in infant and early-childhood mortality lagged behind that for adults by a few decades, and therefore that its causes might have been fundamentally different. In fact, current evidence indicates that his suggestion, that 'improved nutrition' was the underlying factor in the overall decline, now appears to have been essentially correct for the much earlier decline in adult mortality, especially due to tuberculosis. However, the current consensus is that changing reproductive patterns, occasioned by a changing socio-cultural and perhaps legal environment, related to child labor laws, lay behind the much later and very rapid decline in early-life mortality. One must therefore give McKeown great credit for his grasp of both the importance of nutrition, and of the environment, as basic determinants of health.