Objective: To compare the performance of the lecithin/sphingomyelin ratio and the lamellar body count in the prediction of neonatal respiratory distress syndrome. Design: Meta-analysis. Sample: Six studies reporting on the performance of both the lecithin/sphingomyelin ratio and the lamellar body count published between January 1966 and August 1999. Methods: We performed a computerised MEDLINE search to identify articles published on the subject. For the six selected studies, prevalence of respiratory distress syndrome and sensitivity and specificity of the tests in the prediction of respiratory distress syndrome were calculated, and overall performance was assessed by constructing summary receiver-operating characteristic curves. Results: The constructed summary receiver-operating characteristic curves showed the lamellar body count to perform slightly better than the lecithin/sphingomyelin ratio in the prediction of respiratory distress syndrome (P= 0.13). Conclusions: Since the lamellar body count can be performed quickly and since it is less expensive than the lecithin/sphingomyelin ratio, we recommend the former as the test of first choice in the assessment of fetal lung maturity.