In support of the NASA Tropical Rainfall Measuring Mission (TRMM) Ground Validation Program, a suite of surface instruments and vertical pointing Doppler radar profilers were deployed in central Florida to quantify the number and size of the rain drops reaching the surface. Analyzing 276 minutes of simultaneous observations from two surface disdrometers and one profiler revealed good agreement among the instruments for drop sizes >1.5 mm diameter but poor agreement for smaller drop sizes. The magnitude of the difference in small drop estimation was proportional to the reflectivity (and rainrate). At reflectivities greater than 40 dBZ, the differences in the estimation of the number of small drops yielded differences in estimates of mass-weighted diameter of >13% and of rainrate >25%. The combined effect of these uncertainties impact the interpretation of the precipitation processes and the development and validation of space-based precipitation retrieval algorithms. ¿ 2000 American Geophysical Union