This study investigated the potential for head lice transmission in swimming pools using an in vitro experiment and a field trial. In the former study, head lice were submerged for 20 min in aqueous solutions at 25 +/- 1 degrees C: deionized water, sea water, salt solutions (30, 60, 120 and 240 g/l), and chlorinated water (0.2, 2 and 5 mg/l). In all trials, lice located on cut hairs became immobile and did not respond to physical prodding. After entering stasis, no movement was observed until after rescue from submersion and a brief recovery period (0-1 min). Upon recovery, all lice fed and no mortality was observed within the next 4 h. In the field trial, four naturally infected individuals swam in a chlorinated pool for 30 min. No loss of lice or head to head transfer was observed. These results indicated that although head lice survive immersion, head lice transmission is unlikely to occur via the water of swimming pools.