A total of 21 sow herds were randomly chosen to determine the prevalence of vulvar discharge syndrome (VDS) in loosely housed sows. The median VDS prevalence was low as expected, 0% (range 0-4.5%). Nine of the 655 animals examined (1.4%, 95% CI 0.5-2.3) displayed signs of VDS in 21 non-problem herds. In addition, five VDS problem farms were visited to gather more animals affected with the syndrome in order to estimate which methods of examination are useful. Altogether, 19 VDS animals and 19 healthy controls were found, inspected and sampled. Ten of the VDS animals (53%) and three of the controls (16%) were positive in bacterial culture (p = 0.04) taken with a guarded swab from the anterior vagina. In addition, 94% of VDS animals had a positive vaginoscopic examination result and the corresponding figure in the control sows was 28% (p < 0.0002). Cytological smears were classified as positive in 37% of the case sows and in 5% of the control sows (p = 0.04). Detection of vulvar discharge was associated with vaginoscopic examination findings (p = 0.0005) and with bacteriology (p = 0.04), but not with leucocyte counts (p = 0.07). Susceptibility testing was performed on pure bacterial cultures. Totally, 7 (44%) of 16 isolates were considered to be resistant or showed intermediate susceptibility to at least one of the antimicrobial agents tested (sulpha-trimethoprim and ampicillin). In conclusion, we found vaginoscopy and bacteriology as valid tools in diagnosis of VDS and susceptibility testing of antimicrobial treatments was found to be indicated.