Background: Vitamin D is a key hormone in the metabolism of calcium and phosphorus, as well as the creation and maintenance of the mineralized skeleton. It has also been linked to the etiology of autoimmune disorders such as diabetes mellitus type 1 and multiple sclerosis. Vitamin D has been the topic of several difficult investigations in recent years, including its function in the pathophysiology and development of many rheumatological disorders such as rheumatoid arthritis and systemic lupus erythematosus (SLE). Objective: To investigate Vit D sufficiency status in different rheumatological diseases. Patients and methods: The current study included 80 patients, divided into 20 patients with rheumatoid arthritis, 20 patients with SLE, 20 patients with osteoarthritis and 20 patients with other miscellaneous rheumatological diseases. The following investigations have been done. 25(OH) vit D, CRP, ESR, ANA, Ca, Po4, rheumatoid factor , C3,C4 Results: 60% of the studied patients had vitamin D deficiency, 33.75 % had vitamin D insufficiency, 6.25% had sufficient vitamin D.Vitamin D was significantly deficient in patients with rheumatoid arthritis compared to other studied rheumatological diseases, Also vitamin D level was significantly deficient with increasing age and Longer duration of the disease (P value < 0.001). Vitamin D was significantly deficient in patients on corticosteroid therapy and smoker patients. Conclusion: 25(OH) vitamin D was significantly low in Egyptian patients with different rheumatological disease especially rheumatoid arthritis, explaining its role in development of inflammation and autoimmunity. So, 25(OH) vitamin D should be put in consideration in diagnosis and treatment of such patients.