InXenopus laevisoocytes EF−1&agr; is concentrated in a small region of the cytoplasm, known as the mitochondrial mass or Balbiany body. When the mitochondrial mass disperses in early vitellogenic oocytes EF−1&agr; becomes evenely distributed in the cytoplasm. The local concentration of EF‐1&agr; in oocytes probably results from the association of EF‐1&agr; and EF‐1&bgr; with tubulin. Three observations are in favor of this interpretation. First, a large fraction of EF−1&agr; inX.laevisoocytes occurs as a complex with EF−1&bgr;&ggr;. Second, purified EF‐1&ggr; has a strong affinity for tubulin. Third, tubulin is extremely concentrated in the mitochondrial mass and disperses exactly at the same stage of oogenesis as EF−1&agr;. A similar association has been recently postulated between tubulin and an EF‐1&agr;‐like protein located in the centrosphere of sea urchin eggs.