In fifty adult females undergoing lower abdominal surgery for gynaecological cancer the serum gamma globulim level was found to be the single factor displaying the strongest linear association with the requirements of tubocurarine expressed in mg/m2 body surface, r=0.48. Total serum globium displayed an almost equally strong linear association with the same relaxant, r=0.47. In a similar series of fifty patients it was found that for the requirement of alcuronium expressed in mg/m2body surface, the serum albumin level was the most importyant determinant, r=0.62. For both relaxants body surface was a slightly better indicator than body weight. The age and the type of cancer did not influence either the gamma globulins or the tubocurarine requirements. Older patients as well as patients with ovarian cancer had low albumin levels and low alcuronium requirements.