A reliable method for assessing ichthyosis severity has not been uniformly agreed upon. The objective of our study was to develop and validate a tool to measure the clinical severity of the congenital ichthyoses, the Congenital Ichthyoses Severity Index. A prospective study was performed to determine reliability of three Likert scales to evaluate clinical severity of ichthyosis. Thirty-eight subjects recruited from the Foundation for Ichthyosis and Related Skin Types National Conference were evaluated separately by two blinded investigators using the Likert scales. Subjects were then asked to evaluate themselves using these scales. Inter-rater reliability was determined between ratings provided by all three raters. Test-retest validation was conducted with 21 subjects who completed follow-up surveys 4 weeks later. Our severity scales had excellent inter-rater and test-retest reliability as determined by intraclass correlation coefficients (ICC >0.7), with the exception of our hyperkeratosis scale, which demonstrated moderate test-retest reliability (ICC = 0.4). This pilot study provides a promising method for evaluating clinical severity of the congenital ichthyoses, one easily employed by both physicians and patients. Future epidemiologic studies may benefit from use of this instrument, as well as studies evaluating emerging therapies for ichthyosis.