Psoriasis is a common, chronic, immune mediated inflammatory disease that involves the innate immunological system and acquired immunological system. Intracellular calcium plays an important part in the regulation of proliferation and differentiation of keratinocytes. This study tried to identify the correlation between severity of disease and serum calcium level in psoriasis patients. To assess the serum calcium level in patients of different types of psoriasis and to find out its relationship with disease severity according to Psoriasis Area Severity Index (PASI).This cross sectional study was conducted among purposively selected 45 patients in the Department of Dermatology and Venereology, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka who had psoriasis on the basis of history, clinical findings and laboratory report. Regardless of gender, the age ranging from 18-65 years and having no calcium metabolism disorder or impaired renal function were the selection criteria of study participants. All patients were interviewed by Pre-structured questionnaire. Blood sample (5 ml) was collected from each subject and was preserved and analyzed for serum calcium level by the automated analyzer i.e. Beckman Coulter-AU680 in the Department of Biochemistry, BSMMU. Age range of the participants were 18 to 65 years (mean age=34.1±12.1 years). Maximum 26 (57.8%) patients had normal calcium level, 19 (42.2%) patients had hypocalcaemia and no patient was found with hypercalcaemia. As observed, hypocalcemia frequency is high in more severe types of psoriasis. Hypocalcaemia was found among all types of psoriatic patients'. The correlation between PASI and