The efficacy of 18 disinfectant teat dips was tested on teats artificially contaminated with a milk suspension of Staphylococcus aureus. A solution of Na hypochlorite with 40 g/l available chlorine was significantly more bactericidal than one containing 1 g/1 available chlorine and than most other disinfectants tested. The method was not able to distinguish differences in efficacy between solution containing 40g/1 and 10g/1 available chlorine nor between these and some of the iodophors containing 5 g/1 available iodine. The additon of 190-416 g/1 (15-33% v/v) glycerol significantly reduced the bactericidal properties of 3 iodophors (5 g/1 available iodine), but soluble lanolin at approximately 20 g/1 did not appear to lower the efficiency of NaOC1 (45 g/1 available chlorine) or of an iodophor (5 g/1 available iodine).