Ion channels underlie the electrical activity of cells. Calcium channels have a unique functional role, because not only do they participate in this activity, they form the means by which electrical signals are converted to responses within the cell. Calcium channels play an integral role in excitation in the heart and shaping the cardiac action potential. In addition, calcium influx through calcium channels is responsible for initiating contraction. Abnormalities in calcium homeostasis underlie cardiac arrhythmia, contractile dysfunction and cardiac remodelling. Reactive oxygen species participate in the development of pathology by altering the redox state of regulatory proteins. There is now good evidence that reactive oxygen species regulate the function of calcium channels. In this mini-review, the evidence for regulation of calcium channels by reactive oxygen species and implications with respect to pathology are presented. Calcium channels may represent a target for intervention during hypoxic trigger of arrhythmia or chronic pathological remodelling.