In this prospective study we investigated the frequency of vulvovaginal candidiasis, the results of yeast cultures and detection of ketoconazole resistance in female children and adolescents with type 1 diabetes mellitus (DM1). The study consisted of 35 patients with DM1 (age 1.7-20 years) and 22 controls (age 1.5-18 years). Age, duration of DM1 and evidence of genital symptoms were recorded initially. After a pelvic examination, two separate swabs and samples for blood glucose and hemoglobin A,, (HbA(1c)) were taken. One of the swabs was used for direct examination and the second was placed on Sabouraud's dextrose agar and incubated. In vitro susceptibility of Candida species to ketoconazole was established by using Etest (AB BIODISC). Candida species were isolated in 32 of 61 (52.5%) swabs of patients with DM1 and five of 22 (18.2%) of the control group. The predominant Candida species isolated from patients with DM1 were C. albicans (72.7%), C. glabrata (22.7%), C. tropicalis (2.3%), and C parapsilosis (2.3%). The mean HbA(1c) in diabetic patients from whom Candida species were isolated was significantly higher than that of patients without Candida infection (p = 0.002). Most of the C glabrata isolates were significantly resistant to ketoconazole. During the follow-up of patients with DM1, genital candidiasis is generally overlooked. It should not be forgotten that species other than C albicans might cause genital candidiasis.