The C-12/C-13, N-14/N-15, and S-32/S-34 isotope ratios in comet Hale-B
opp (C/1995 O1) were determined through observations taken with the Ja
mes Clerk Maxwell Telescope, Measurements of rare isotopes in HCN and
CS revealed isotope ratios of (HCN)-C-12/(HCN)-C-13 = 111 +/- 12, (HCN
)-N-14/(HCN)-N-15 = 323 +/- 46, and (CS)-S-32/(CS)-S-34 = 27 +/- 3. Wi
thin the measurement uncertainties, the isotopic ratios are consistent
with solar system values. The cometary volatiles thus have an origin
in the solar system and show no evidence for an interstellar component
.