The interaction of soft x-rays with poly(butene-1 sulfone) (PBS) has been examined in detail, using monochromatized synchrotron radiation from the Canadian Synchrotron Radiation Facility (CSRF). The total photoabsorption cross section and neutral fragment yields of poly(butene-1 sulfone) (PBS) were measured over the photon energy range 20 ≤ hv ≤ 1000 eV. Energy deposition in this energy region results primarily in mass loss due to depolymerization. The chemical byproducts were detected using an in situ mass spectrometer. The experimental absorption data was corrected for spectral contamination of the incident monochromator radiation through the use of calculated photoabsorption cross sections. The calculations incorporated reliable dipole oscillator strength distributions of smaller molecules chemically related to PBS as input, and the results are reliable over the absorption regions away from the edges. The corrections thus applied to the initial experimental data have produced the most reliable spectrum available presently for PBS. The near-edge extended x-ray absorption fine structures (NEXAFS) were measured and assigned for the sulfur 2p (L2,3), carbon 1s (K) and oxygen 1s (K) edges. The sulfur 2p edge of PBS was found to be very similar to that found in the photoabsorption spectrum of gaseous SO2, particularly in the continuum region. The two broad peaks in the continuum have been assigned as σ*-shape resonances caused by a centrifugal potential barrier. Ionization of the valence orbitals of PBS produced a significant increase in the depolymerization reaction, and subsequent neutral yields of sulfur dioxide (SO2) and 1-butene. © 1993 John Wiley & Sons, Inc.