The newly developed system of polyacrylate-polymethacrylate-coated charcoal, filled in a column has been tested for its efficiency in removing theophylline, as a model drug both from a buffer solution pH 7.4 and human plasma using a closed-circuit apparatus. Preliminary testing determined the capacity of the charcoal column and the effect of circulation rate of the buffer solution on the clearance of theophylline. It was found that the circulation rate does not significantly affect the clearance rate of theophylline, while the concentration of drug in the buffer solution has a considerable effect on the clearance of the drug, presumably due to the saturation of the column. The clearance of the drug from plasma in comparison to buffer solution was also investigated. It was found that more than 70 per cent of the drug was removed from the buffer solution within the first 15 min as compared with 65 per cent from plasma; with 95 per cent removed from buffer after 1 h in comparison to 93 per cent from plasma. The blood compatibility of the polymer was studied by incubating various concentrations (5-25 per cent w/v) of the polymer in blood for 30 min at 25-degrees-C. A concentration of 5 per cent polymer was also incubated for a series of incubation times. The results indicated that with polymer concentrations up to 15 per cent there is no significant lysis of RBCs in comparison to a blank. This concentration of the polymer is much higher than that required to coat 200-300 g of charcoal with a 4 per cent coating, which in turn will not exceed 0.145-0.218 per cent w/v of polymer in the entire blood volume of 5.51 present in the human body.