Digitoxin may be determined polarographically in amts. as low as 0.1[mu]g. in alcohol or blood. Half wave potentials are in the region between -1.9 and -2.0 volts. Errors in detn, in the range of 0.1-0.4[mu]g are [plus or minus] 0.02[mu]g. For detns. in blood, the glycoside is extracted from the blood with petroleum ether and evaporated to dryness. The residue extracted with absolute alcohol and then diluted to 50%. 0.2 N tetraethyl-ammonium hydroxide is added to the extent of 10% of the final volume.