This brief overview outlines recent progress in our understanding of the regulation of cell population size, focusing on some important developments in cell cycle control and the recognition of the importance of growth arrest and cell death. Histopathologists, and others with an interest in tissue architecture, have much to offer to those who study the biochemical and molecular processes of proliferation, growth arrest and cell death, and these processes are unlikely to be understood simply by analysis of in vitro systems and cell lines. Such biochemical and histological information may well feed back into clinical medicine in terms of new approaches and techniques, new reagents and new paradigms. With regard to the application of measures of proliferation, growth arrest and cell death as prognostic factors or other diagnostic tools, we are sceptical. Methods for assessing cell proliferation seem unlikely to be implemented widely in practice since there is little direct evidence that they are really an improvement on conventional histological assessment, optimally employed. But, there again, we may be proved wrong! In particular, it may be that, if carefully employed, assays that integrate information about death, growth arrest and proliferation may be clinically valuable.