A new species of Spirillum has been isolated from grass cuttings. Main characters: vacuoles and volutin granules; motile by lophotrichous or amphitrichous flagella; no spores; Gram-negative; good growth in 0·5% Evans peptone; no growth in meat extract or grass infusion; inhibited by 0·5% (w/v) sodium chloride; catalase-negative; microaerophilic; good growth at 4°: optimum temperature 28°. The species has been designated Spirillum mancuniense.