Latex isolated from laticifer cells of Euphorbia lathyris maintained its ability to synthesize triterpenols (and their esters) from acetate. When the latex was centrifugated at 5 000 g for 15 min. this biosynthetic activity could be subdivided into two separate fractions; the acetate to β‐hydroxymethyl glutaryl‐coenzyme A activity remained in the supernatant, while the β‐hydroxymethyl glutaryl‐coenzyme A to triterpenol activity was pelleted. Further purification of the pellet by isopycnic centrifugation on Percoll gradients yielded at least three particles: latex particles, starch grains, and a single membrane‐bound organelle. Electron micrographs were made of all of these latex particles. The single membrane‐bound organelle was only observed in the region of the density gradient that exhibited the ability to incorporate mevalonic acid into the triterpenoids. In addition, the enzyme β‐hydroxymethyl glutaryl‐coenzyme A reductase (EC 1.1.1.34) was found in the 5000 g pellet, while β‐hydroxymethyl glutaryl‐coenzyme A lyase (EC 4.1.3.4) remained in the supernatant.