We have studied the influence of clinical concentrations of propofol (2,6-diisopropyl phenol), emulsified propofol (Diprivan) and the emulsifier of propofol (Intralipid 10%) on random and chemotactic locomotion of human polymorphonuclear leucocytes in an agarose assay. Random locomotion was decreased (P < 0.001) to a similar extent by the three drugs. Concentrations of propofol 2.5 mug ml-1 and greater, and of Diprivan 3.33 mug ml-1 and greater, also reduced chemotaxis (P < 0.05) against both zymosan-activated human serum (C5a) and N-formyl-methionyl-leucyl-phenylalanine (FMLP), used as chemoattractants. Intralipid reduced chemotaxis towards C5a but not towards FMLP. We conclude that propofol in clinically relevant concentrations may adversely affect leucocyte locomotion in vitro.