To determine if amniotic fluid interleukin-10 (IL-10) concentrations are elevated in women with labor, either at term or preterm, and in the setting of infection-associated preterm labor, amniotic fluid samples were collected from women: (1) at term, not in labor (n = 42); at term, in labor (n = 56), preterm contractions, undelivered within 1 week (n = 22), and preterm labor, delivered within 1 week (n = 31). IL-10 concentrations were assayed in each sample via ELISA (Pharmingen, San Diego, CA). In a subsequent analysis, 8 women with preterm labor associated with chorioamnionitis were matched for gestational age with women experiencing preterm contractions (undelivered within 7 days) and preterm labor (delivered within 7 days) and amniotic fluid IL-10 concentrations compared. Approximately 40-70% of amniotic fluid samples obtained from women in each group had detectable IL-10. However, there were no significant differences in amniotic fluid IL-10 concentrations among the patients. While 1 of 8 patients with chorioamnionitis had amniotic fluid IL-10 concentrations greater than 300 pg/ml, there were no statistically significant differences among the matched samples. Amniotic fluid IL-10 concentrations were not elevated in women with term labor, preterm labor, or chorioamnionitis. This finding contrasts with the elevated concentrations of pro-inflammatory cytokines and chemokines such as interleukin-1, tumor necrosis factor-alpha, IL-6, IL-8, MIP-1 alpha, and GRO alpha reported in previous studies. Because we did not detect elevations of the key anti-inflammatory cytokine IL-10 in amniotic fluid of women with infection-associated preterm labor, we suggest that anti-inflammatory processes in this setting may be attenuated.