Point processes and random measures find wide applicability in telecommunications, earthquakes, image analysis, spatial point patterns, and stereology, to name but a few areas. The authors have significantly reshaped their first edition of 1988 and now present Introduction to the Theory of Point Processes in two volumes sub-titled "Elementary Theory and Models" and "General Theory and Structure". Volume One contains introductory chapters and offers new material on marked point processes and processes evolving in time, where the conditional intensity methodology provides a basis for model building, inference, and prediction. Volume Two returns to the general theory, with additional material on marked and spatial processes. The necessary mathematical background is reviewed in appendices located in Volume One.