OBJECTIVES: To map the Insomnia Severity Index (ISI) to the EQ-5D utilities. METHODS: A cross-sectional, online survey was conducted among adult US residents with self-reported sleep problems. Respondents provided demographic, comorbidity, previous-night sleep-related information and, completed the EQ-5D and the ISI, a seven-item instrument measuring perceived insomnia severity. Each ISI item is scored from 0-4 with minimum total score of 0 (no insomnia) and a maximum of 28 (most severe insomnia). Respondents can be classified into four ISI categories (0-7: no clinically significant insomnia; 8-14 subthreshold insomnia; 15-21: moderate insomnia; 22-28: severe insomnia). Generalized linear models were used to map the seven ISI items (Model 1), the ISI summary scores (Model 2), and the four ISI clinical categories (Model 3) onto EQ-5D utilities. Predictions were estimated using 50/50 split sample validation. Model fits were assessed using mean squared error (MSE) and distributional quality of predicted values. RESULTS: Respondents (n=2,842) were predominantly middle-aged, female, Caucasian, with ≥1 comorbidity. Mean sleep duration was 7.8 (±1.9) hours, mean ISI score was 14.1 (±4.8). Mean predicted utilities were (0.765±0.08) across all models, overlapping with observed utilities (0.765±0.18). Using Model 1, predicted utilities increased linearly with improving ISI (0.493 if ISI=28; 1.00 if ISI=0, p<0.01). In Model 2, each unit decrease in ISI summary was associated with a 0.022 (p<0.001) increase in utility. Predicted utilities were 0.868, 0.809, 0.722 and 0.579 for no clinical, subthreshold, moderate and severe insomnia, respectively (Model 3). The overall MSEs between predicted and observed utilities were good in all models (Model I: 0.025, Model II & III: 0.026), especially when predicting utilities >0.40 (MSEs: 0.016-0.056). MSEs were higher when predicting lower utilities (MSEs: 0.138-0.156). CONCLUSIONS: Linear relationships were found between EQ-5D utilities and the ISI. These relationships can be used to estimate the impact of insomnia-associated treatment effects on utilities.