In almost all cells, cytosolic Ca(2+) is a crucial intracellular messenger, regulating many cellular processes. In non-excitable as well as in some excitable cells, Ca(2+) release from the intracellular stores into the cytoplasm is primarily initiated by the second messenger inositol 1,4,5-trisphosphate (IP(3)), which interacts with the IP(3) receptor (IP(3)R), a tetrameric intracellular Ca(2+)-release channel. This review focuses on the pharmacological modulation of the various functionally important sub-domains of the IP(3)R, including the IP(3)-binding domain, calmodulin-binding sites, adenine nucleotide-binding sites and the sites for interaction for FK506-binding proteins and other regulators. We will particularly focus on the pharmacological tools that interfere with these domains and discuss their relative specificity for the IP(3)R, thereby indicating their potential usefulness for unraveling the complex functional regulation of the IP(3)R.