The optical spectra of chlorophyll a and chlorophyll b in PMMA and MTHF were studied over a wide range of concentration (8 X 10-6-1 X 10-3 mole/l in PMMA, and 10-6-10-1 mole/l in MTHF). In the absorption spectra it is possible to identify bands which originate from chlorophyll disolvates and chlorophyll monosolvates in MTHF as well as bands which are most probably due to isolated chlorophyll molecules in PMMA. In high-concentration samples of chlorophyll in MTHF some bands may be assigned to aggregates, but based on optical results only, no particular model can be proposed. The emission spectra are strongly influenced by reabsorption and energy transfer processes. However, the so-called Qy band of isolated molecules in PMMA and of chlorophyll monosolvates in MTHF as well as the Qx and the Qy bands of chlorophyll disolvates in MTHF can be identified unequivocally in the fluorescence spectra.