It is true to say that it is just over the past decade and even more so in this new decade that it has become appreciated how vitally important vitamin D is for optimum health. This ‘sunshine’ vitamin could justifiably be called ‘the nutrient of this decade’. Until recently, vitamin D was known primarily for its role in bone health. However, as a result of advances in research this perspective has changed. While it is true to say that the classic function of vitamin D is to control calcium and vitamin D metabolism, we now know that the importance of vitamin D spreads far wider than just bone health. There is much ongoing research with regard to its emerging role in immunopathology, as a potent inhibitor of cellular growth, stimulator of insulin secretion, modulator of immune function and inhibitor of renin production. This review discusses the current evidence with regard to the clinical consequences of vitamin D deficiency and underscores the fact that physicians should be vigilant in searching for and treating this preventable and treatable condition. Furthermore, this review highlights the fact that the time is opportune for rheumatologists to agree upon clinical guidelines to advise practitioners as to when and in which patients to check for, what target vitamin D level to aim for and how best to treat vitamin D deficiency.