Measurement of the ratio of branching fractions B(D0→π-e+νe)/B(D0→K-e+νe)

Using 3.0 fb-1 of data collected with the CLEO-II detector, we study the Cabibbo-suppressed decay D0→π-e+νe. The ratio of the branching fractions B(D0→π-e+νe)/B(D0→K-e+νe) is measured to be (10.3±3.9±1.3)%, corresponding to an upper limit of 15.6% at the 90% confidence level.