"Lysosomes are now known tobe notjustacollectionofisolatedorganellesofin- terest only to the biochemist, but part ofa complex, dynamic, membranous sys- tem essential to the cell's economy." So wrote the late Dame Honor Fell and I in the preface to the first volume of Lysosomes in Biology and Pathology almost 30 years ago. We wentonto say thatresearchonthelysosomalsystematthetimewas in a state ofexplosive and chaotic growth. While the chaos has beenlargely reduced, the growthofresearch into the bi- ology ofthe lysosome remains considerable. Biologists worldwide are still fasci- nated by the diversity of activities and the interaction between the various membranous systems of the cell, both in biological and pathological situations. The present volume, edited by John Lloyd and Robert Mason, who have each made major contributions to research in this field, continues to systematize the growthofinformation in this importantarea. Taken together, the twelve chaptersofthis volume form an extensive update ofour knowledge of the biological and physiological role of the lysosomal sys- tem. The book will enhance our knowledge ofcell function and help in our un- derstanding ofthe factors that control cell metabolism in health and disease. John T. Dingle Hughes Hall Cambridge, England ix Preface Lysosomes are still orphan organelles. Even in the 1990s, it is not unknown for members of a scientific or medical audience to reveal, by a question following a lecture, thatthey confuse lysosome with lysozyme or liposome.Andthis ignorance has adeeperreasonthan mereconfusionoversimilar-sounding terms. Itarisesbe- cause Iysosomes exist on the periphery of cell function, rather than at its center.