During the period 1973 to 1979 the number of recorded incidents of equine salmonellosis increased from 23 in 1973 to a peak of 111 incidents in 1976, but has since decreased to 32 in 1979. Of the 416 incidents recorded during the period of the survey 292 were caused by Salmonella typhimurium and 121 by 33 different serotypes; in three instances rough strains of salmonella were involved. The number of incidents caused by serotypes other than S typhimurium increased from one in 1973 to 32 in 1976. The number of different salmonella serotypes increased from two in 1973 to 23 in 1977 and has subsequently declined. Drug resistance monitoring of salmonella strains from horses showed that most of the strains were resistant to streptomycin and sulphonamides, although resistance to other antibacterial drugs used was low. Seventeen different patterns of antibiotic resistance were observed but resistance to more than two antibiotics was uncommon.