This study evaluated the use of amniotic fluid (AF) glucose concentration as a rapid indicator of intra-amniotic infection. Amniotic fluid glucose concentrations were measured in 86 pregnancies and compared with AF cultures. There were 14 positive cultures with a mean AF glucose of 7.1 mg/dL (range 1-24) and 72 negative cultures with a mean AF glucose of 30.4 mg/dL (range 5-66), a significant difference (P less than .001). An AF glucose of less than or equal to 5 mg/dL had a positive predictive value of 90%; an AF glucose of greater than 20 mg/dL had a 98% negative predictive value. Amniotic fluid glucose can be obtained rapidly and inexpensively, and may be of use in the diagnosis of intra-amniotic infection.