The reports contained in this volume of abstracts comprise three cate gories of papers presented at the Third International Congress of Histo chemistry and Cytochemistry. The format of the meeting called for a series of Plenary Sessions on each of the five mornings of the Congress as follows: I. Recent Developments in Cytochemical Localization by Electron Microscopy. 2. Centrifugal and Electrophoretic Techniques in Histochemistry. 3. New Directions in Quantitative Cytochemistry by Physical Techniques. 4. Subcellular Structural-Functional Correlates. 5. Current Developments of Histochemistry...