Seeds of Avena sativa were grown in the dark in wet vermiculite at 22/sup 0/C. When the seedlings were 16 days old, the primary leaf was cut into pieces. These leaf pieces were put 25-ml Erlenmeyer flasks in 10 ml glycylglycine with and without PbCl/sub 2/, and preincubated in the dark for 1 h. The flasks were held for 72 h at 21/sup 0/C in a water bath, illuminated at 7000 lux, and shaken 40 times a minute. Chlorophyll was extracted and the content of chlorophyll a and chlorophyll b determined. Synthesis of both types of chlorophyll was reduced in proportion to the increasing amounts of lead ions. Even concentrations as low as 50 ..mu..M PbCl/sub 2/ had a statistically significant effect. At lower concentrations (0-500 ..mu..M) synthesis of chlorophyll b was inhibited to a greater extent than that of chlorophyll a; at higher concentration the chlorophyll a and chlorophyll b were about the same. 7 references, 1 figure.