This paper summarizes the basic steps to be taken in the assessment of historical masonry structures. It also includes a brief discussion on temporary emergency interventions to be made. The paper emphasizes the importance of a sound assessment and diagnosis prior to any permanent intervention, like repair or strengthening. Although assessment and diagnosis should be made by experts, especially for old masonry structures, and although each case presents a unique problem, the author believes that some flexible rules and a check list can be drafted.