Four years of weather observations from ships in the World Meteorological Organization Voluntary Observing Program were compared with common parameters measured simultaneously by NOAA moored buoys when ships were within 100 km of buoy stations. Common parameters were wind speed, wind direction, atmospheric pressure, surface air and sea temperatures, wave height, and wave period. From a data base containing as many as 63,354 pairs of ship-buoy reports (in the case of wind speed), the analysis provided an overall set of difference statistics as well as separate sets of difference statistics for each of the following data categories to reveal possible correlations: year, season, geographical region, buoy location, and separation between ship and buoy to a distance of 100 km. The results showed little correlation with any of these subcategories. Ship-reported wind speeds were on average 2--4 kn higher than buoy-reported winds, with standard deviations of 7--8 kn (1 kn=0.51 m/s). Mean differences in wind direction of about 7¿ and standard deviations of direction differences of 45¿ were typical. Mean differences and standard deviations of differences for the remaining parameters were atmospheric pressure (-0.5 mbar, 4.2 mbar), air temperature (1.1 ¿C, 4.3 ¿C), sea temperature (0.1 ¿C, 3.5 ¿C), wave height (0.1 m, 2.2 m), and wave period (-0.2 s, 2.4 s). Factors responsible for these differences are noted, particularly for surface winds. This analysis represents the first known quantitative comparison of simultaneous observations made by ships and buoys for such a large data base. ¿ American Geophysical Union 1990