Glycerol was tested as an agent to promote hyperhydration of male and female subjects. Series I experiments involved ingesting 0.5, 1.0, or 1.5 g glycerol/kg body wt and within 40 min drinking 0.1% NaCl, 21.4 ml/kg. In series II, 1.0 g glycerol/kg body wt was ingested at time 0, and 25.7 ml/kg of 0.1% NaCl was ingested over a 3.5-h period. Experiments were of 4-h duration and included controls without glycerol as each subject served as his/her control. Blood samples were taken at 40- or 60-min intervals for hemoglobin (Hb), hematocrit (Hct), plasma osmolality, glycerol, and multiple blood chemistry analyses. Urine was collected at 60-min intervals. Glycerol ingestion increased plasma osmolality for 2 h and reduced the total 4-h urine volume. There were no significant changes in Hb or Hct as a result of the glycerol or excess fluid intake. This study demonstrates that glycerol plus excess fluid intake can produce hyperhydration for at least 4 h.