This work presents current knowledge of the molecular genetics of the protein factors relevant to venous thrombotic disease, and describes the molecular basis of the various known deficiency states. It brings together all the relevant information required for the identification, study and analysis of the underlying gene/protein defects. It covers protein structure, function and biochemistry, gene structure and expression, as well as epidemiological and molecular aspects of the deficiency state. Molecular models of the proteins and their dysfunctional variants are presented wherever possible.