The authors describe a scale designed to measure five dimensions of delusional experience: conviction, extension, bizarreness, disorganization, and pressure. Reliability was adequate to excellent on four of the dimensions, but only fair on the dimension of bizarreness. In 52 delusional patients, no two dimensions correlated highly with each other, indicating that the dimensions were not redundant. Factor analysis identified two factors from the five dimensions--delusional involvement and delusional construct. On the basis of these results the authors suggest that delusions are a multidimensional phenomenon; the results have implications for the measurement of delusions in clinical research and for the understanding of the structure of psychotic experience.