Transformed roots are also called transgenic roots or due to their appearance ? hairy roots. Transformed roots are obtained by infection of plants or parts of them with soil bacteria, Agrobacterium rhizogenes. Genetically transformed roots are characterised by rapid and stable growth of biomass, genetic stability, and stable biosynthesis of metabolites. Hairy roots can be an alternative source of many economically important chemicals like enzymes, pigments, flavours and especially bioactive pharmaceuticals. Cultures of transformed roots are comparatively easy to cultivate in shaking flasks. Application of flasks does not allow to obtain great amount of biomass. There is a necessity of scaling up the culture using bioreactors. The first attempts of scaling up the culture were connected with bioreactors designed for microbiological processes. However, these bioreactors are inadequate for hairy roots cultures. Some promising results were achieved in the case of using mist bioreactor. This paper is a review of bioreactors employed in cultures of hairy roots and mathematical modelling of hairy root growth.