In the review the basic bioactive substances of spirulina and their influence on the immune function of organisms were discussed. Spirulina, the blue-green microalgae, contains both the unique well-balanced complex of nutrients and the range of bioactive compounds which are able to condition the innate immunity and promote an adaptive immunity. The basic effects of spirulina in various forms on mammals, particularly humans, were analyzed. Owing to the nutritive quality, relatively low costs and almost absence of adverse reactions, the spirulina is of great interest for food and drug industry.