Chemical signals are the language of information exchange among the cells of the body. These signals, which bind to receptors to relay information into the cell, include hormones, neurotransmitters, growth factors, and cytokines. The relay of information is referred to as signal transduction. Information that is transduced into the cell may elicit short term responses such as contraction, secretion, or a change in metabolic processes. Alternatively, the signals may direct long-term responses involving differential gene expression and cell growth. Signal-mediated information exchange is essential for cellular homeostasis and coordination of all body functions. Defects in cellular communication and signal transduction are the molecular basis of cardiovascular dysfunction and pathology. Present and future therapeutic medical and nursing interventions will be based on this emerging paradigm. This article describes how chemical signals transduce or transfer information from the outside to the inside of the cell. This information provides theoretical background for the other articles in this and the next issue of The Journal of Cardiovascular Nursing, which will discuss the role of cell signaling in specific pathologic conditions or interventions.