Squamous cell carcinoma (SCC) in situ or Bowen's disease (BD) is a slowly progressive malignancy. However, cases of regression have been reported. Recent reviews cover only certain aspects of this disease; therefore, this paper's aim is to cover all the relevant aspects for medical practice, such as clinical, histological and therapeutic details. BD may affect all regions of the skin and mucosa, but in accordance with the region and etiologic factor, it may embrace different clinical forms, some of them very similar with other skin lesions. Dermoscopy may prove useful for establishing a clinical diagnosis. Several patterns have been encountered and may help distinguishing from other diseases. When in doubt, puncture biopsy or complete excision may be performed in order to obtain histological data that could define BD. Different morphological aspects of the involved components are described in order to reduce the risk of misdiagnose. In order for the approach to be complete, relevant information about treatment has been presented, underlining the pros and cons of each available therapy.