DIR couplers were first introduced in 1972, in Kodacolor II, and since then the demand for both higher sensitivity and higher image quality in color negative films has increased. Additionally, the demand for preserving good image quality on color prints for a long time is significant. To satisfy these requirements, many kinds of couplers, including functional couplers such as DIR, DSR and BAR couplers, have been investigated. Furthermore, recent progress in the study of new classes of couplers, that will enable us to improve color image quality in the future, is worthy of attention.