Mesosystems associated with stationary radar echoes were analyzed. Five of them occurred on 20 July 1956 over the area of the U. S. Weather Bureau's Severe Local Storms Network, and they grew to 300–400 mi in diameter. Divergence and vorticity at each 1000-ft level inside a composite mesosystem were computed up to 5000 ft. It is found that the wind field is rotational up to 3000 ft where it becomes irrotational. Appreciable divergence reaching over 100 × 10−5 per sec on the ground decreases linearly to 30 × 10−5 per sec at the 5000-ft level. Computed vertical velocity inside the mesosystems was about 1 ft per sec at 1000 ft, reaching 3 ft per sec at the 5000-ft level. A small system of 13 August 1947 over the Thunderstorm-Project area was also studied; it was only 20 mi in diameter. Comparison of the characteristics of these systems indicated that the systems, large and small, may be produced by similar processes.