Movement of recreational boats in a waterway such as the Upper Mississippi River System (UMRS) may generate waves of sufficient degree to impact the river biota and the stability of the shorelines. A research project aiming to determine the characteristics of waves generated by recreational craft within the UMPS has been completed, and this is the first of a two-part paper that presents results. Part II presents the results of uncontrolled movement. To meet the objectives of the project, 246 controlled runs were made with 12 different boats at two sites, one on the Illinois River and the other on the Mississippi River. Data from this study indicated that recreational boats can generate from 4 to 40 waves per event, with a mean of about 10 to 20 waves. These waves can last from 6 to 40 seconds or more. On the average, wave heights for these controlled events varied from 0.06 to 0.52 m, with the maximum value as much as 0.6 m. A regression equation was then developed for estimating maximum wave heights on the basis of boat speed, draft and length, and distance. This relationship can be used to determine wave heights generated by recreational boats in natural rivers and lakes.