Shilajit is a multi-component natural occurring mineral substance used in Ayurveda and Siddha systems of medicine which originated in India. Its source can be traced to the mountainous regions, where the hilly tribes first identified its beneficial use. Shilajit is aptly referred to as 'rasayana'/'rasayanam' in Ayurveda and Siddha literature which means rejuvenator because it prevents ailment and enhances the quality of life. An attempt has been put forth to review shilajit pertaining to its origin, synonyms, varieties, physical properties, chemical constituents, therapeutic properties and important biological properties to affirm its rasayana property. All relevant information on shilajit was collected from classical texts including pharmacopoeias, formularies, etc. Moreover, select doctoral thesis from Banaras Hindu University, Varanasi and Gujarat Ayurved University, Jamnagar were also scanned. Published papers on shilajit were collected from important databases for biomedical sciences. Amongst, the various biological properties of shilajit, antioxidant activity and immuno-modulatory activity were focused as it is closely related to its rasayana potential. This review finds that shilajit is used in twenty Sastric formulations and twenty-four proprietary drugs for extraneous indications. Even-though, there is a long history of use of shilajit in traditional Indian materia medica, shilajit unfortunately lacks scientific evaluation and systematic documentation. In vivo antioxidant activity of shilajit has been studied at an irrelevant dose and without using a positive control. The immuno-modulatory activity does not stand the test of critical assessment and currently may be considered as unproven. Based on the earlier studies, the bioactivity of shilajit lacks substantial evidence. Nevertheless, further studies are imperative to overcome the lacuna in establishing the antioxidant property of shilajit and more specific assays are needed to vouch shilajit as an immuno-modulator which may be of use to establish its rasayana potential. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.