Zinc markedly stimulated growth ofVerticillium albo-atrumR. & B. in Czapek-Dox broth shake cultures. Minimum zinc concentration producing optimum growth response was 0.15 to 0.2 μg/ml. On a dry weight basis added zinc resulted in increased total nitrogen content and oxygen uptake. Oxygen uptake per unit total nitrogen was essentially unaffected. Cells from 5- and particularly 7-day-old zinc-free cultures showed less response to zinc than did those from 3- and 10-day-old cultures. Zinc response was greatest withL-alanine as the nitrogen source as compared with nitrate, urea, and ammonium nitrate sources.