Background: The use of biologics to treat moderate to severe psoriasis is increasing. Before using biologics, a considerable disease period often precedes. Objectives: We investigated treatment pattern up to the start of biologics for psoriasis (PsO). Methods: We conducted a study using Korean National Health Insurance System Claims Database from 2008-17. Systemic agents and phototherapy utilization patterns before biologics were analyzed in 531 PsO and PsA patients who started ustekinumab(UST) and TNF-α inhibitor(TNFi). Results: 6% had PsA(UST: 3.3%, TNFi: 9%). While UST were treated with more cyclosporine(CyS, 76.4% and TNFi were treated with more methotrexate(MTX, 77.7%). Medication pattern of mono/dual/triple therapy were 50.8%, 32.4%, 16.8%, respectively. TNFi had higher total dose (0.55g) and duration (394 days) of MTX than UST (0.33g, 276 days). The duration of CyS were: <6 months (52.5%); 6-12 months (22.9%); 1-2 years (13.7%); ≥2 years (10.8%). The total dose of MTX were:<1g (88.6%); 1-2g (8.4%); 2-3g (2.1%); ≥3g (0.9%). 92 patients (17.3%) underwent phototherapy. The mean duration of total treatment before using UST and TNFi were 501.4, 539.7 days, respectively. Conclusion: Most patients were treated appropriately according to the guidelines, but some were treated more excessively. We think that it is needed to consider the appropriate transition period for the severe PsO patients who require rapid disease control.