Optical coherence tomography (OCT) is a new noninvasive imaging technique. In this study, it was used for the investigation of contact dermatitis and psoriasis. In these common inflammatory skin diseases the value of OCT for quantification and monitoring of the changes in comparison with other bioengineering methods was evaluated. Repeated measurements were performed in healthy volunteers after experimental induction of irritant contact dermatitis and in patients with psoriasis. In the OCT images, the thickness of the epidermis and the signal attenuation coefficient in the upper dermis were evaluated. The changes were compared with measurements of transepidermal water loss, hydration, skin colour and surface roughness, and with high-frequency ultrasound measurements. In irritant dermatitis and psoriasis, thickening of the epidermis was detected and could be monitored over time. The light scattering in the upper dermis was lower than in healthy skin. This was interpreted to be due to the inflammation and oedema, leading to a less-dense arrangement of the collagen fibres. The changes in the OCT images did not significantly correlate with the changes shown by the other methods. OCT is an interesting tool for investigation of inflammatory skin diseases. It is a simple method for determination of epidermal thickness and therefore provides, in addition to other methods, information on the severity of the disease and on treatment effects.