A large study of the distribution of Clostridium difJicile in the environment of the Cardiff area of South Wales was performed with a methodology designed to maximise recovery. A total of 2580 samples was taken, with 184 (7.1%) yielding isolates. The highest yield for C. d i f f i l e was obtained from river waters, with 14 (87.5%) of 16 samples from four rivers positive, and from sea water samples with 7 (44%) of 15 positive from six beaches on the Bristol Channel. In addition, 7 (46.7%) of 15 samples of lake water were also positive. Twenty-two (21%) of 104 soil samples, taken from random sites in Cardiff, were positive, as were 20% of environmental samples from four Cardiff hospitals. C. difficile was also isolated from 50% of eight swimming pool waters examined and 1 (5.5%) of 18 of mains tap water. Carriage of C. difficile in 524 faecal samples of assorted farm animals was c. 1%, and was 10% in dogs and 2% in cats. In private residences, the organism was present in 12 (2.2%) of 550 samples. While 2.4% of 300 raw vegetable samples were positive, none of 107 assorted fish gut contents was. These findings indicate that C. difficile may be more widely distributed in the general environment, particularly water, than was previously thought.