Abstract: Artificial competence of Synechococcus PCC 6301 cells was induced by lysozymetreatment and the cells were transformed to chloramphenicol resistance with foreignplasmid pBR 325 at a frequency of approximately 5?0-5 or 5?0-4 with the transformant DNA. The transformation frequencies were higher than those reported byother workers for the same strain with cloned DNA employing a physiological transformation system.Analyses of DNA electrophoresis,secondary transformation anddot blotting demonstrated that foreign plasmid had integrated into the recipientchromosome by a single crossover event.The results showed that the artificial transformation system was efficient and reproducible. Conditions that affected transformation,such as,incubation time of cells with DNA,age of the cells,light or darkincubation were also studied.