BACKGROUND. Background speech is a common disturbance in offices, especially in open-plan offices. Background speech influences performance and subjective estimations. However, not many studies have examined simultaneously physiological, performance and psychological consequences background speech has on humans. AIM. To examine the influence of background speech on subjective experience, performance, and physiological measures. METHODS. We examined the influence of background speech compared to silence in a between-group laboratory experiment. We tested 40 subjects: 21 subjects in the speech group and 19 subjects in the silence group. Background speech was a radio dialogue played at 65 dBA level, which people were supposed to ignore while making cognitive tasks and answering questionnaires. Background speech condition lasted for 50 minutes. Participants’ performance, subjective experience and various physiological stress reactions (e.g. stress hormone level, heart rate variability) were measured. RESULTS. Compared to the silence group, the speech group had lower performance and higher physiological stress level. Speech was subjectively estimated more annoying and loading, but less tiring than silence. PRACTICAL IMPLICATIONS. This study shows that background speech influences experience, performance, and physiological stress level. Therefore, its influence should be minimized in offices, where work requiring concentration is needed.