Bacteriophage λ, a virus infecting  Escherichia coli cells, is one of model organisms in molecular biology. Studies on λ DNA replication provided very important, basic data about the mechanisms of initiation of replication of genetic material. However, after many years of studies on this subject, there are still unsolved questions about specific mechanisms controlling replication of bacteriophage λ DNA. In this mini- review, we summarize recent progress in understanding phenomena that lead to regulation of this process, and discuss problematic points that still require further studies to be solved. Particularly, we focus on the mechanisms of the switch from early to late mode of λ DNA replication, structure and function of the heritable λ replication complex, and a role for transcription from p_R and p_O promoters in the regulation of DNA replication initiation from oriλ.