Abstract Background: Hypertension may develop early, before the age of 40 years, in both genders, so-called young-onset hypertension. The clinical characteristics of young-onset hypertension have not been well defined. Methods: The personal history and clinical characteristics were evaluated in a series of patients with young-onset hypertension. With the individual-matching, case-controlled design, patients were initially matched for age, gender and residence with the first control (C1) group in either 2:1 or 1:1 fashion. They were then additionally matched for body mass index (BMI) with the second control (C2) group in 1:1 fashion. To elucidate the possible difference between genders, all the comparisons were conducted in males and females separately. Results: A total of 82 consecutive patients, 56 males and 26 females, with young-onset hypertension were included. Compared with the 148 subjects in C1 group, hypertensive patients were relatively highly educated and had less alcohol drinking in either gender. BMI (25.10±0.49 vs. 22.34±0.31 kg/m 2, P<0.001) and serum triglyceride level (153.35±10.71 vs. 98.76±5.12 mg/dl, P<0.001) were significantly increased in male patients, while serum uric acid (5.74±0.34 vs. 4.78±0.17 mg/dl, P=0.006) and triglyceride level (121.39±12.71 vs. 76.58±4.88 mg/dl, P=0.002) were increased in female ones. Compared to that in C2 group, serum triglyceride level was still increased in patients of either gender. Interestingly, serum cholesterol level in female patients was lower than that in either C1 or C2 group. Further, serum triglyceride level was significantly correlated to BMI, serum cholesterol and glucose level in male patients but only to serum uric acid level in female ones. Conclusions: Clinical characteristics of young-onset hypertension were unique and different by gender. Though consistently increased in patients of either gender, serum triglyceride level was correlated to BMI, serum cholesterol and glucose level only in males, suggesting the gender-specific presence of metabolic syndrome in young-onset hypertension.