This issue ofThe Journal of Nervous and Mental Diseasereports fundamental research into the nature of mental disorders, using both new and traditional time-sampling approaches. The studies present convincing findings gathered in a variety of patient popula tions and demonstrate the utility of using quantitative and replicable methods in psychiatric research and clinical care. Research that adequately describes the person in context as well as the influence of situations on mental state has proved difficult. Methods such as the diary and Experience-Sampling Method that explore experiences in daily life overcome some of the shortcomings of previous psychiatric research strategies, such as reliance on retrospective recall and the failure to take the variability of mental state more fully into account. The studies in this issue introduce techniques for creating a data base for psychiatric research and clinical practice that is anchored in patient experience and behavior.