To survey clinical characteristics at diagnosis for children diagnosed with Type 1 diabetes during 25 years in the south-east part of Sweden we included all 1903 children < 16 years of age and who had been diagnosed between 1977 and 2001 in the south-east region of Sweden. A nurse or doctor in the diabetes team obtained information from medical records. Over the 25 years the mean duration of symptoms prior to diagnosis was 17.8 +/- 26.4 days and the mean glucose level at diagnosis was 23.6 +/- 9.7 mmol/l. Three percent of the children (n = 50) had a pH value < or = 7.1. The youngest children (0-5 years) had shorter duration of symptoms, lower blood-glucose levels and less often had ketonuria than the oldest children (11-15 years) but more often suffered from infections prior to diagnosis. The proportion of children diagnosed in the group 0-5 years of age increased over the study-period, apart from the last 5 years, while children with pH value < or = 7.3 decreased significantly as did the proportion of children with ketonuria or infection. The clinical characteristics at diagnosis of diabetes are heterogeneous, especially in the oldest age group. Some characteristics varied with time.