sic theater singers (MTS) typically have a heavy vocal load, but the impact on their voices has not been previously evaluated. A group of 49 MTS from two professional productions were administered the Singing Voice Handicap Index (SVHI). Responses for the SVHI demonstrated that, although the SVHI supported the performers self-report of healthy vocal status, it lacked the sensitivity to detect potential subtle fluctuations or changes in physical functioning of the voice for working singers. Secondarily, descriptive data regarding professional working singers perspectives were collected regarding how their singing voices typically responded to performing in a music theater production after a show, across a working week, and across a production season. Seventy-nine currently performing MTS were involved in a series of focus group interviews (n = 43) or a written survey (n = 36) to detail their perception of the impact of performing in an eight-show per week professional production on their vocal function and vocal health. Thematic analysis revealed the MTS commonly perceived transient and variable changes in their singing voice status in both positive and negative directions after heavy vocal load. Based on these data, a list of 97 descriptors of these perceptual changes was generated using the singers own terminology and experiences. These included symptoms of vocal impairment and vocal fatigue but also some novel descriptors of positive vocal changes to the physical functioning of the singing voice as a perceived consequence of heavy vocal load. This study offers new and valuable insights into performers perceptions of the impact of performing in a musical theater production on physical aspects of vocal function. ? 2013 The Voice Foundation.