Quantitative and qualitative microbiological studies were conducted in a vertical laminar airflow surgery and in a conventional surgical theater. Samples were collected at floor levels within each surgery and also at the wound. Microorganisms recovered from the floor site were gram-positive cocci and gram-positive nonsporeforming rods, with considerably fewer numbers of gram-negative rods, Bacillus species, and molds. The predominant species recovered at the wound site were gram-postive cocci and gram-positive nonsporeforming rods. The level of airborne viable particles was higher in the conventional surgery than in the laminar airflow surgery, both within the room and at the incision. The same types and percentages of microorganisms found in samples collected at the floor level were found at the wound site in the conventional surgery.