After twenty years of clean-air operating rooms, no uniform opinion about the efficiency in preventing infections has been achieved. The reason is that with an infection rate around 1% only very large series of homologous material are statistically significant. Vertical flow is more efficient than horizontal flow. Clean-air technique is only one of the many facets of antisepsis and asepsis; it should be used especially in implantation and transplantation surgery in spite of the fact that its efficiency is not yet clearly proven.