1. 1. Sodium dodecyl benzene sulphonate (SDBS) extracts have been prepared from higher plant and Euglena chloroplasts having varying chlorophyll a : chlorophyll b ratios. Chloroplasts from a mutant of barley lacking chlorophyll b have also been examined. 2. 2. Discrete chlorophyll-protein complexes were separated by polyacrylamide gel electrophoresis of the extracts. The proportion of chlorophyll associated with pigment-protein complex I was similar whatever the chlorophyll a : chlorophyll b ratio of the starting material. The proportion of the total chlorophyll bound to pigment-protein complex II varied between 0 and 45%. 3. 3. Loss of chlorophyll from pigment-protein complex II resulted in the formation of the apoprotein which, upon electrophoresis, migrated as a band of lower molecular weight than the pigment-protein complex II. 4. 4. The presence and amount of pigment-protein complex II and of its apoprotein correlated with the chlorophyll b content of the starting material.