Table of contents : Introductory remarks....Pages 1-4 Aspects of the geometry of twistor space....Pages 5-15 Massive systems and their internal symmetries....Pages 16-28 Twistor quantization: Zero rest mass fields....Pages 29-42 Twistor quantization: Massive fields....Pages 43-55 The low-lying baryons....Pages 56-71 Mesons, resonances, and bound states....Pages 72-93 Leptons and weak interactions....Pages 94-107 Sheaves and cohomology....Pages 108-125 Applications of complex manifold techniques to elementary particle physics....Pages 126-146