Theoretical and experimental aspects of using radio scintillation to study ionospheric irregularities will be reviewed in this paper. Both weak and strong scintillation theories will be presented. Theoretical results will be compared with typical experimental data to demonstrate the procedure. Discussions will be concentrated on what information about ionospheric irregularities can be extracted from scintillation data and how. Also, a recently developed simulation technique for radio wave propagation through ionospheric irregular structures will be discussed. It will be shown that by applying this technique, one can obtain information about the properties of the irregularities that are of either statistical or deterministic nature. Specific examples of applying this technique to study equatorial ionospheric bubbles will be reviewed.