The influence of maternal diabetes on Group B Streptococcus (GBS) colonization and GBS urinary infection was investigated. The population under study comprised 1,050 pregnant women (70 of them diabetics, the remaining 980 non-diabetics). A higher prevalence of GBS colonization was found among diabetics (20% versus 10.9%) (p less than 0.05). The rate of colonization was not correlated to the severity of the diabetes condition. Urinary infection was diagnosed on 8.6% of diabetic patients, versus 7.1% of non-diabetics (p greater than 0.05). Urinary infection by GBS occurred with similar frequency in both groups (0% in diabetics and 1% in non-diabetics). The possible etiological implications are commented on, and vaginal and rectal cultures are recommended for GBS screening in the pregnant diabetic patient.