Background: Quantification of skin diseases can be carried out in many ways. Clinical scores are widely used in atopic eczema (AE), and noninvasive instruments are a relevant supplement. Objective: Our purpose was to validate 5 noninvasive instruments in quantification of AE severity. Methods: In all, 101 patients with AE and 30 control subjects were assessed twice in a clinical cross-sectional examination. Assessment of transepidermal water loss, stratum corneum hydration, erythema, scaling, and subepidermal edema was assessed on 3 predetermined skin sites. Results: The methods discriminated among various severity degrees and correlated significantly with objective assessment of disease severity. High correlations were found among instruments assessing acute symptoms of AE. Threshold values for transepidermal water loss and capacitance were found. Limitations: No gold standard exists for severity assessment of atopic eczema. Therefore, the methods used cannot be validated in relation to such a standard. Furthermore, atopic eczema is a generalized disease and the methods used assess target lesions. By assessing target lesions, information about the disease is reduced. Conclusion: Noninvasive instruments are valuable in quantification of disease severity in a mixed group of patients with active AE. Assessment with ultrasound has contributed new information about the pathophysiology in AE.