From the German preface of R. Remmert: "When kings build their kingdom, there is work for the draymen. Kiyoshi Oka was a king. His kingdom was the function theory of several complex variables. He solved problems which were believed to be unsolvable; he developed methods whose audacity brought the admiration of the mathematical world. Oka gave new life to complex analysis." This book comprises Oka`s ten Mémoires with comments by Henri Cartan.