Abstract We have compiled a bibliography of papers dealing with triplet-triplet absorption spectroscopy which we hope is reasonably complete through April 1982. The number of references (about 800) has mandated the separation of this list into two parts. Part A 1 included work published before 1976; Part B from then until the above cutoff date. The initial set of references for the current period was obtained as a subset of a profile on transient spectra matched against our current awareness procedures. This was augmented by various keyword searches of the RCDC bibliographic data base. 2 The keywords (and logic) chosen were (triplet state and absorption spectra) or triplet-triplet absorption or triplet-triplet transition. Further references were secured from the biologically oriented review of Bensasson et al. 3 and from the inspection of the reference lists of a large number of papers targeted by our search strategy. We have included only those papers providing quantitative spectral information such as peak locations and extinction coefficients. Studies in which the observation of a known triplet-triplet absorption is used simply as a kinetic tool have generally been omitted. Work in the gas phase has been excluded and we have not covered the theoretical aspects of the phenomenon. The exact identity of the metastable absorber in coordination compounds is generally uncertain and these have also been excluded from consideration although studies on chlorophylls and porphyrins have been retained. As before internal laboratory reports and conference proceedings have usually been discarded. The resulting list of references has been printed in roughly chronological order.