A solid-phase-radioimmunoassay (SPRIA) for the monitoring of blood digoxin level has been developed, in which a secondary antibody-coated polystyrene tubes are used. This noval method seems to be simple to use and only takes about an half hour. The standard curve is linear from 0.25 to 4 µg/L. The sensitivity of the detection is 0.1 µg/L. Reproducibility studies with 3 control sera of 0.5~2.5 µg/L give intraassay CV< 5% and interassay CV< 10%. The specimens are measured and compared with those of the conventional radioimmunoassay and the values are well correlated (r=0.96, Y=1.022X+0.04 µg/L).