CC16 is a lung secretory protein mainly produced by clara cells. This has been shown to increase progressively in ammniotic fluid during normal pregnancy and it has also been suggested to be a potential marker of fetal lung growth (Pediatr Res 36:771, 1994). Surfactant protein A (SP-A) on the other hand has proved to be a reliable marker in amniotic fluid of fetal lung maturation. Our purpose was to evaluate the possible correlation between CC16 and other known markers of fetal lung maturation such as SP-A, disaturated phosphatidylcholine (DSPC) and the lecythinsphingomyelin ratio (L/S ratio). We measured amniotic fluid concentrations of CC16, SP-A, DSOC and L/S ratio in 53 pregnancies with normal fetuses at 26-38 weeks gestation; CC16 was measured by immunoassay, SP-A by ELISA using a rabbit anthihuman polyclonal antibody, L/S ratio and DSPC by thin layer chromatography, using osmium tetroxide in the latter. As expected, there is a progressive increase of SP-A, DSPC and L/S ratio with gestational age (SP-A, r=0.41; L/S, r=0.48). The poor correlation with DSPC (r=0.02) is probably due to the fact that the most significant increase in these values takes place at the end of gestation; SP-A as well as DSPC correlate well with L/S ratio (r=0.46, p<0.001 and r=0.46, p<0.001 respectively) while CC16 has a weaker correlation with L/S ratio (r=0.32, p<0.02). In our data CC16 also correlates with gestational age (r=0.30, p=0.02); furthermore using multiple linear regression CC16 does not correlate well with gestational age (r=0.30, p=0.02); furthermore using multiple linear regression Cc16 does not correlate to L/S ratio, DSPC or SP-A but only with gestational age (p=0.017). The different markers of pulmonary maturation in amniotic fluid (SP-A, DSPC and L/S ratio) increase progressively with gestational age. Although CC16 also increase, it does in a different manner with very poor or no relation with the other markers. We speculate that CC16 only reflects lung growth and has no apparent relation with pulmonary maturation (Partially supported with FONDECYT Grant N° 1930854).