Background: Psoriasis is a heterogeneous disease with several clinical manifestations; the symptoms are characterized by redness, scaliness and thickness of the skin. There are several treatment options available for psoriasis and patients with moderate to severe psoriasis generally need systemic agents. In 2004 biologics were introduced for patients with moderate to severe psoriasis in Sweden. Methods: The Swedish Health Care Registers and the Swedish registry for systemic treatment of psoriasis PsoReg, were used to; estimate the incidence of psoriasis cases in the Swedish specialist care, to examine the treatment allocation and important factors related to the initiation of especially biologic treatment. Results: On average 9000 new psoriasis patients entered specialist care in Sweden each year under study, corresponding to an incidence of 98 patients per 100,000 person-years. In the treatment allocation analysis of the incident psoriasis cases in the Swedish specialist care Patients living in a Metropolitan Area and with a University degree were more likely to initiate a biologic treatment. By analysing biologic-naïve patients enrolled in PsoReg, PASI (the physician’s assessment of the psoriasis severity) and Psoriasis Arthropathy were shown to be two important factors associated with the initiation of biologic treatment while sex was not. Furthermore, it was also shown that the decision to initiate biological treatment was more strongly associated with PASI than with DLQI (the patients’ assessment of the disease impact Quality of Life). Conclusion: These studies indicate that there are inequalities in the assignments of systemic psoriasis treatments (especially in biologic treatment). Since the allocation of treatments should not depend on sex, education or residency in a Metropolitan Area but rather the need of care, it is important that future studies continue analysing possible factors that could influence the initiation of treatment in clinical practice.