A total of 14 extensively pretreated patients with advanced and progressive malignancy were given 140 infusions of autologous plasma that had been perfused over staphylococcal protein A bound to an agarose gel (Sepharose). Infusions ranged in volume from 35 ml to 260 ml (mean, 70 ml), and the quantity of protein A used ranged from 1 to 30 mg per 100 ml of plasma (mean, 10 mg). Acute toxic reactions included fever (21%), chills (18%), nausea (17%), vomiting (8%), pain (9%) and bronchospasm (2%). Four patients did not have an acute toxic reaction and no chronic or cumulative toxic effects were identified. In two patients there was objective tumor regression and in five there was stabilization of disease lasting from 4 to 12 weeks. Further study of this treatment modality is warranted.