Bullosis diabeticorum (BD) is considered a rare and relatively harmless skin manifestation with tense blisters appearing rapidly and mostly on the feet. Most papers report only a few cases and the cause of the blisters is not known. We have experienced that the lesions are not so rare and may turn into chronic foot ulcers with complications. Retrospective study of 25 consecutive patients with 35 outbreaks and 93 bullae in a population of 5000 people with diabetes treated during a 3-year period. The bullae were deroofed in order to examine the bulla base and treated as foot ulcers including debridement, antibiotics, bandage and protective footwear. The incidence of BD per year in the present diabetic population is 0.16%. In 29 outbreaks, there were hypoglycaemic episodes or highly varying blood glucose. Antibiotics were given in 17 of 35 episodes. Time to healing was as much as median 2.5 months (range 0.5-23 months). Two patients had minor amputations. BD should be well known to all members of diabetic foot care teams. Blood glucose control with special attention to hypoglycaemia at the time of eruption, deroofing of the bullae and foot ulcer care are recommended.