In a naturalistic pre-post design, samples of saliva were collected from the members of a professional chorale during an early rehearsal (n = 31 ) , a late rehearsal (n = 34) and a public performance (n = 32) of Beethoven's Missa Solemllis. As measures of immune system response, mean levels of secretory immunoglobulin A increased significandy, as a proportion of whole protein, 150% during rehearsals and 240% during the perfor mance. Cortisol concentrations decreased significandy an average of 30% during rehearsals and increased 37% during performance. As measured through performance perception rating scales, a group of emotions and other experiential states that singers associated with professional singing were highly predictive of changes in level of secretory immunoglobulin A during the perfo rmance condition, but the results for the rehearsal con ditions were not significant. The best multiple regression model for per formance level of immunoglobulin A (p < .0015) included seven emo tional, cognitive, and evaluative variables generally associated with choral singing, including levels of mood before and during singing, stress, relax ation, feeling "high," detachment/engagement, and specifi c satisfaction with the immediate performance.Received May 27, 1999; accepted March 15, 2000.T HE purpose of this study was to determine whether choral singing is associated with physiological changes in the immune system. A pro fessional chorale was studied during a period in which they rehearsed and performed Beethoven's complex choral masterwork, Missa Solemnis. As described by its practitioners, the successful choral singing experience in public performance is a peak experience during which, in the face of per fo rmance challenges and anxiety, the performer has transcendent feelings