Time profiles and histograms of plasma data from Pioneers 10 and 11 are examined for the period between 1975 and 1983. During this time, Pioneer 10 traveled between a heliocentric distance of 8.7 and 30.4 AU. The velocity structure of the solar wind at these heliocentric distances is found to have one of two distinct forms: Approximately 70% of the time the solar wind has a nearly flat velocity profile. Occasionally, this flat velocity profile is accompanied by quasi-periodic variations in density and in thermal speed consistent with the concept that the ''corotating interaction regions'' which are produced by the interaction of high- and low-speed streams at intermediate heliocentric distances are replaced by ''pressure regions'' in the outer heliosphere. The remaining 30% of the time the solar wind is marked by large (50--200 km/s) long-term (30--120 day) shifts in the average solar wind velocity. ¿American Geophysical Union 1987