A multicentre field study was conducted in accordance with VICH Guideline on Good Clinical Practice (VICH 2000) to confirm the efficacy and safety of a new formulation of cefquinome for the treatment of naturally occurring severe bacterial infections and septicaemia in foals. Thirty-nine foals suffering from severe bacterial infections (such as pneumonia, gastro-enteritis, arthritis, omphalitis, or wound infections) or acute septicaemia were treated twice daily with the test product (1 mg cefquinome/kg body weight) intravenously for three days and then intramuscularly for three to 11 days. Investigators examined the foals daily and scored both systemic and local clinical signs to assess the response to treatment, treatment success and relapses. On the day of inclusion a blood sample was taken from each foal for IgG determination and blood culture. In case of abnormal clinical findings additional samples were taken for bacteriology. Treatment was successful in 87.2% of cases (34 of 39 foals) and no relapses were observed. The average duration of treatment was 7.5 days. At inclusion, bacterial culture was positive in 40.5% (15 out of 37) of the blood cultures. Escherichia coli, Clostridium perfringens and Staphylococcus spp. were the most common isolates and were all susceptible to cefquinome. E. coli predominated in swabs from umbilical and open wound infections, and in rectal swabs E. coli. There was no correlation between IgG at inclusion and study outcome or treatment duration. The test product was very well tolerated by all of the foals following intravenous and intramuscular injection. The cefquinome formulation tested was effective and safe in the treatment of severe bacterial infections and septicaemia in foals under field conditions.