Background: Psoriasis and psoriatic arthritis are common, chronic, immune mediated disease of the skin and joints. Interaction between genes and environment are important in disease causation. Objectives: The aim of the present study was to determine the socioemographic and clinical characters of adult patients with psoriasis and those with psoriatic arthritis, to define psoriasis and psoriatic arthritis etiological risk factors, and to define the relationship between psoriasis severity and these items. Subjects and methods:This study was conducted at Dermatology Clinic, Al-Hussein University Hospital. A case-control study design was chosen to perform this research. The study was conducted on 100 adult patients with psoriasis and an equal number of free adults as controls. Criteria for diagnosis of psoriasis and psoriatic arthritis were used. A comprehensive questionnaire was used to survey the studied groups. Body surface area of the affected patients was used as a marker of disease severity. Results: The study showed that 44.0% of the cases had psoriasis age of onset; 22-45 years. Stress was the most common etiological risk factor, 67.0%. While, the most important risk factors were family history of psoriasis, recurrent pharyngitis, smoking ≥20 cigarettes/ day and higher level of education, odds ratio (OR)=7.58, 5.94, 2.78 and 2.69, respectively. Also, 32.0% of the patients had psoriatic arthritis. Psoriatic arthritis comes after psoriasis and had mild severity in 65.6% and 68.7% of the cases, respectively. The most important etiological risk factors were severe psoriasis, smoking ≥20 cigarettes/day and early onset of psoriasis, OR=9.64, 3.06 and 2.72, respectively. Conclusions and recommendations: The epidemiology of psoriasis is not well defined in Egypt. The heredity and environmental factors are the most important risk factors. Also, psoriatic arthritis is an important associated disease. The fact that it has no cure has important implications for how it should be viewed, prevented and treated. We recommend that more research should be carried out to understand the true epidemiological features of the disease in Egypt and its impacts on quality of life of the patients.