This work reports the results of a systematic series of measurements of speech propagation between workstations in a conventional open-plan office. The propagation measurements were repeated as the parameters describing the open-office configuration were systematically changed. The values of the following were varied: workstation panel height, panel absorption, workstation plan size, ceiling height, and ceiling absorption. In addition the effects of the location and type of ceiling light fixtures were investigated as well as details of the workstation furnishings and configuration. The results are evaluated in terms of Speech Intelligibility Index values, SII (ANSI S3.5 1997). The SII is a new version of the articulation index and is a weighted speech-to-noise ratio that is a good measure of the expected speech privacy. The height of the partial height panels separating workstations and the absorption of the ceiling have the most important effects on speech privacy. Workstation size, panel absorption, and lighting configuration have intermediate effects on speech privacy. Ceiling height and workstation configuration had smaller effects on expected speech privacy.