The functional MRI (fMRI) procedure has several sources of variance that determine the success of the examination. These include the scanner, patient, and paradigm. As blood oxygenation level dependent (BOLD) contrast is a small effect, high signal-to-noise performance is mandatory. Because the preparation of a functional activation map requires averaging multiple images over time, the scanner must produce high temporal stability of the signal intensity. This unit presents the Basic Protocol for achieving scanner stability. There are many determinants of such performance but not all possibilities need to be checked separately. An adequate approach has been to verify total system performance under the conditions of a functional MRI study on a phantom. This testing is done daily prior to patient studies.