The incorporation of UDP-galactose-l4C into lipids of spinach chloroplasts as affected by different experimental conditions was studied. It was found that the use of a pyrophosphate buffer and the addition of albumine during isolation and incubation of chloroplasts enhance the incorporation of UDP-galactose-14C compared with other buffers or no addition of albumine. Furthermore, the ability of chloroplasts to incorporate UDP-galactose decreased with the age of the chloroplasts. The rate of UDP-galactose incorporation into lipids of the chloroplasts appears to depend on the condition of the chloroplasts.