In the article entitled "Circulating Placental RNA in MaternalPlasma Is Associated with a Preponderance of 5' mRNA Fragments:Implications for Noninvasive Prenatal Diagnosis and Monitoring"by B.C.K. Wong, R.W.K. Chiu, N.B.Y. Tsui, K.C.A. Chan, L.W.Chan, T.K. Lau, T.N. Leung, and Y.M.D. Lo (Clin Chem 2005;51:178695),there is an error in the section on "2-step RT-PCR" on page1789. For random priming, the thermal profile should read "25°C for 10 min, 48 °C for 30 min, and 95 °C for 5min," with the omission of "of 25 cycles." Similarly, for oligo(dT)priming, the thermal profile should read "40 °C for 10 min,48 °C for 30 min, and 95 °C for 5 min," with the omissionof "of 25 cycles." The authors apologize for any confusion thismay have caused.