Three methods for immune complex detection were used on 85 women who took oral contraceptives and on 21 who took none to test their sera for circulating immune complexes. The methods were ammonium sulphate precipitation as proposed by Beaumont et al., polyethylene glycol precipitation, and the 125J-Clq fixation test. - Significant rise in precipitable proteins, in excess to anything recordable from women with no oral contraceptives, was established from the oral-contraceptive group only by means of 25-per-cent ammonium sulphate precipitation. No significant difference between the two groups could be measured by the two other techniques. - Ammonium sulphate precipitation is not specific of immune complexes, and no difference between the two groups was recordable by means of the 125J-Clq fixation test, a technique more specific of immune complexes. The conclusion, therefore, was drawn that the proteins which had caused rise in ammonium sulphate precipitation had been proteins of unspecific precipitability rather than immune complexes. - Findings so far obtained are likely to suggest that administration of oral contraceptives will hardly induce formation of circulating immune complexes.