This paper presents a high-resolution X-ray photoemission spectrum of the valence bands of gold, obtained using monochromatized Al Kα radiation and a single-crystal specimen. The results were compared with theoretical density-of-states functions, and several conclusions were drawn: 1. Relativistic band structure calculations are necessary to fit the experimental spectrum. 2. Both the KKR calculation by Connolly and Johnson and the RAPW calculation by Christensen and Seraphin provide density-of-states results that closely follow the experimental curve after broadening. 3. Full Slater exchange is required; fractional exchange (2/3 or 5/6) results in d-band densities of states that are too wide. 4. Eastman's 40.8 eV ultraviolet photoemission spectrum is similar to the X-ray spectrum, suggesting little dependence on photon energy above 40 eV. 5. These findings imply an absence of strong matrix-element modulation in the photoemission spectrum. The experimental procedures and results are described in detail, including data reduction steps such as smoothing, background subtraction, and inelastic scattering correction. The theoretical comparisons highlight the importance of relativistic effects and full Slater exchange in understanding the gold valence bands. The paper also discusses the implications of these findings for ultraviolet photoelectron spectroscopy (UPS) and the comparison of X-ray photoelectron spectroscopy (XPS) spectra with theoretical band-structure calculations.This paper presents a high-resolution X-ray photoemission spectrum of the valence bands of gold, obtained using monochromatized Al Kα radiation and a single-crystal specimen. The results were compared with theoretical density-of-states functions, and several conclusions were drawn: 1. Relativistic band structure calculations are necessary to fit the experimental spectrum. 2. Both the KKR calculation by Connolly and Johnson and the RAPW calculation by Christensen and Seraphin provide density-of-states results that closely follow the experimental curve after broadening. 3. Full Slater exchange is required; fractional exchange (2/3 or 5/6) results in d-band densities of states that are too wide. 4. Eastman's 40.8 eV ultraviolet photoemission spectrum is similar to the X-ray spectrum, suggesting little dependence on photon energy above 40 eV. 5. These findings imply an absence of strong matrix-element modulation in the photoemission spectrum. The experimental procedures and results are described in detail, including data reduction steps such as smoothing, background subtraction, and inelastic scattering correction. The theoretical comparisons highlight the importance of relativistic effects and full Slater exchange in understanding the gold valence bands. The paper also discusses the implications of these findings for ultraviolet photoelectron spectroscopy (UPS) and the comparison of X-ray photoelectron spectroscopy (XPS) spectra with theoretical band-structure calculations.