Despite the emphasis placed on occupational impairment as a consequence of most sleep disorders, there is currently no standardized measure for quantifying the occupational impact of sleep quality at the individual level. Using existing scales, a comprehensive literature review, and focus groups to generate items, as well as psychometric analyses to reduce items, these analyses describe the development of a scale to assess workplace performance in relation to sleep quality. In a survey of 222 employees aged 20 to 64 years, the resulting 19-item instrument (the Loughborough Occupational Impact of Sleep Scale [LOISS]) showed satisfactory levels of reliability, effective discrimination between "good" and "poor" sleepers, and an interpretable 2-factor structure. LOISS provides a practical tool for population screening and clinical assessment.