&NA;In order to evaluate the most reliable means of determining fetal maturity, six amniotic fluid components were analyzed from 99 women who were 22 to 40 weeks pregnant. The six parameters investigated were: amylase activity, the lecithin to sphingomyelin (L/S) ratio, percentage of fat cells, and the concentrations of protein, creatinine, and bilirubin. In general, single components and combinations of two or three of the tests did not significantly enhance the predictive accuracy or reduce the error from that obtained with the L/S ratio used alone.