The Experience Questionnaire, a research instrument measuring experiential data, was derived from literature on peak performance and peak experience, with constructs extended to comprise negative extremes of performance and feeling. The efficacy of the Experience Questionnaire is tested by addressing accessibility and salience of experiential data and independence of construct events. Data on construct events (peak performance, peak experience, flow, average events, misery, and failure) were gathered from 123 adults. Since over-all event effects were significant on repeated-measures multivariate analysis of variance, discriminant analysis and analysis of variance with repeated measures were used. Construct independence and salience of experiential data are supported by correct classification of 97.7% of construct events and differences among construct events on factor and item scores that provide clear, differential descriptions. Peak performance is characterized by full focus and self in clear process. The role of other people is unimportant. Peak experience is noted for fulfillment, significance, spirituality, and the importance of other people. Play, other people, and outer structure, but not spirituality, are endorsed in flow. Average events have outer structure, but full focus is a negative correlate. Misery is characterized by spirituality and significance, but other people, playfulness, and self in clear process are denied. Failure is characterized by spirituality but lacks fulfillment.