The incidence of ‘specific’ and ‘non-specific’ antiglobulin antibodies was determined among 648 multiparous females, 213 recipients of intramuscular anti-D immunoglobulin and 221 recipients of intravenous plasma anti-D. Results obtained six months after the administration of anti-D showed that the formation of ‘specific’ anti-Gm or anti-Inv was no greater in recipients of anti-D immunoglobulin or plasma anti-D than in the controls. The incidence of ‘non-specific’ antiglobulins increased from an expected 5% among recipients of intravenous plasma anti-D to almost 25% in mothers given intramuscular anti-D immunoglobulin. It is suggested that the raised ‘non-specific’ antiglobulins may be provoked by a residue of aggregated Y-globulin components which is known to be present in preparations of Cohn fraction II. Six months after the passive administration of Rh antibodies residual anti-D activity was more, often observed in recipients of intramuscular anti-D immunoglobulin than in recipients of plasma anti-D.