The experiments have shown that although butter of exceptionally fine flavour can be produced by the use of pure culture starters of S. paracitrovorus under laboratory control, the uncertainties under practical conditions, due to its weak growth, are too marked to warrant its general use. Both S. citrovorus and S. paracitrovorus are unable to compete successfully with the inevitable contaminants encountered in practice. The value of vegetable media such as grass, silage and bean agar for growing streptococci such as S. paracitrovorus has been confirmed, but as observed by Orla-Jensen et al. the subsequent growth in milk media lacks the vigour which might be expected.