Renewed interest in the study of star clusters and associations has been aroused by at least three developments.

(a) Interpretation of the color-magnitude (C-M) diagrams of clusters and associations with a theory of stellar evolution promises to give data on galactic structure problems. Information of kinematic relations, origins, and past history of stars over the face of the H-R diagram will be available when proper evolutionary interpretation is achieved. Only by assembling C-M diagrams of many clusters of different ages and richness can the empirical approach to evolution be fully exploited.