Mannose-binding lectin (MBL) is an acute-phase serum protein, and its inherited deficiency has been shown to predispose to infections. The developmental profile of serum MBL in preterm infants has been demonstrated previously. To determine the profiles of serum MBL levels and mbl2 polymorphisms over age and genders in an adult population, samples from 689 southern Chinese (age range 16-57 years; 382 males and 307 females) were studied using enzyme-linked immunosorbent assay and high-throughput genotyping of mbl2. Serum MBL levels maintained within a narrow range from age groups of 16-20 years old to 31-40 years old (mean of 2050-2160 micro g/l) and declined to a mean of 1466 micro g/l in the last age group 41-57 years old. No significant differences were found in the distributions of mbl2 haplotypes (YA, XA and YB) among all these age groups. Between gender groups, no significant imbalance of MBL profile in terms of serum MBL levels and distribution of mbl2 haplotypes was found. Results suggest an important role of circulating MBL in first-line host defence because MBL maintains at fairly constant levels after childhood and no gender influence on the MBL profile.