It is becoming increasingly clear that an understanding of congestive heart failure hinges on the study of endocrines, particularly the adrenals and the pituitary, and on the knowledge of physical-chemical properties of the contractile proteins. Much has been accomplished in recent years in elucidating the relationship between the endocrines and heart failure; paradoxically, however, the role of the heart muscle in eliciting the chain of events leading to congestive heart failure remains very much in dispute. There is still disagreement on the physical-chemical properties of material prepared from normal heart muscle, particularly on those prepared from the failing heart. Much of this disagreement is the result of divergence of techniques and of preparations used. It is the purpose of this review to describe these techniques briefly and to discuss possible causes for the differences in results obtained by various investigators. Results from this laboratory will be included which deal with