A preliminary assessment of the impact of the ERS 1 scatterometer wind data on the current European Centre for Medium-Range Weather Forecasts analysis and forecast system has been carried out. Although the scatterometer data results in changes to the analyses and forecasts, there is no consistent improvement or degradation. In this sense, the impact of the data is neutral. Our results are based on comparing analyses and forecasts from assimilation cycles which are identical in all respects except that the control experiment uses no scatterometer data. The experiment period runs from 0000 UT, December 26, 1991, through January 2, 1992. The two sets of analyses are very similar except for the low level wind fields over the ocean. Impacts on the analyzed wind fields are greater over the southern ocean, where other data are scarce. For the most part the mass field increments are too small to balance the wind increments. The effect of the nonlinear normal mode initialization on the analysis differences is quite small, but we observe that the differences tend to wash out in the subsequent 6-hour forecast. In the northern hemisphere, analysis differences are very small, except directly at the scatterometer locations. Forecast comparisons reveal large differences in the southern hemisphere after 72 hours. Notable differences in the northern hemisphere do not appear until late in the forecast. Overall, however, the southern hemisphere impacts are neutral. The experiments described are preliminary in several respects. In light of expected refinements to the scatterometer model function, the ambiguity removal algorithm and the analysis procedures, we expect these data to ultimately prove useful for global data assimilation. ¿ American Geophysical Union 1993