Objectives: We sought to describe the development of an instrument to quantify the stringency of state indoor tanning legislation in the United States, and the instrument's psychometric properties. The instrument was then used to rate the stringency of state laws. Methods: A 35-item instrument was developed. An overall stringency measure and 9 stringency subscales were developed, including one measuring minors' access to indoor tanning. Stringency measures showed good internal consistency and interrater reliability. Results: In all, 55% of the 50 states and the District of Columbia had any indoor tanning law, and 41% had any law addressing minors' access. Oregon, Illinois, South Carolina, Florida, Indiana, Iowa, and Rhode Island had high overall stringency scores, and Texas and New Hampshire were the most restrictive with regard to minors' access. Limitations: Measurement of actual enforcement of the laws was not included in this study. Conclusions: The instrument appears to be an easy-to-use, reliable, and valid methodology. Application of the instrument to actual laws showed that, in general, state laws are relatively weak, although there was considerable variability by state.