Clara cell protein (CC16) is an endogenous anti-inflammatory agent. It is produced mainly in the respiratory and urogenital tracts. CC16 has been quantified in serum, but not in cerebrospinal fluid (CSF). The aim of this study was to examine CSF CC16 in relation to age, gender and serum CC16, and to examine CC16 levels in parturients. If CC16 levels are increased with age and during pregnancy, it may be responsible for the attenuation of inflammatory diseases such as multiple sclerosis during these conditions. CC16 was measured in CSF and serum taken just before Caesarean section (n=33) or just before an elective surgical procedure in females (n=52) or males (n=31). Fetal serum, amniotic fluid, and maternal urine were also sampled during Caesarean section. CC16 levels in CSF did not differ between parturients and an age and gender matched non-pregnant group, but was higher in male than in female patients. There was a significant and positive relationship between age and CSF CC16 levels and between serum and CSF CC16 levels. Fetal CC16 was significantly and positively correlated with amniotic fluid CC16. The present study suggests that CC16 found in CSF originates from passive diffusion from blood, and that CC16 found in amniotic fluid is derived from the fetal lung. During pregnancy, CC16 does not appear to contribute to alterations which occur in the progression of inflammatory disorders.