Effects of some physical and chemical factors on the germination of akinetes of Anabaena cylindrica were studied. The akinetes placed in an inorganic medium germinated, after a certain lag period, in the light but not in the dark. At temperatures above 35°, no germination occurred even in the light. This germination was inhibited by 3, 4-dichlorophenyldimethylurea (DCMU), an inhibitor of photosynthesis. The optimum pH for germination in the inorganic medium was in the range of 7.0 to 8.0. Oxygen was essential for the germination of akinetes. Among various compounds tested, acetate was most effective in stimulating the germination. Acetate was easily taken up by akinetes, but it did not affect the respiration. Radioactivity of the incorporated ¹⁴C-acetate was mainly recovered in ethanol-soluble fraction, especially in glutamate and leucine.