The hyperfine structures of five optical lines of 65-hour radioactive Hg197 and 25-hour isomeric Hg197* were measured. Radioactive mercury produced by cyclotron bombardment and excited in electrodeless discharge tubes containing as few as 5×1012 atoms, free of natural mercury, gave adequate light intensities. The analysis of the hyperfine structure confirmed the magnetic dipole moment and isotope shift of Hg197 in its ground state (I=12), and gave the following values for Hg197* (based on I=132):μ197*=-1.04+/-0.01 nm; Q197*=(1.5+/-0.3)×10-24 cm2; isotope shift displacement (from Hg198 in the 2537 A line)+70+/-7×10-3 cm-1. Thus an isomeric shift of atomic energy levels resulting from the excitation of the nucleus from its ground state I=12 to the isomeric state I=132 is observed. In the 2537 A line of mercury this shift amounts to -21+/-6×10-3 cm-1.