Field experiments were established on September 7, 1968, and Hay 13 and July 16, 1969, by seeding three rates (on pure live seed basis [PLS]) of several companion grasses with a constant rate of Kentucky bluegrass (Poa pratensis L.). Mixtures were irrigated and clipped to 1- and 2-in. sod residues. Objectives were to determine which mixture or mixtures could provide rapid initial establishment. with subsequent high quality, permanent turf. The improved perennial ryegrasses (Lolium perenne L.) (NK-100 and Pelo) were no more competitive in the seedling stage toward Kentucky bluegrass (Poa pratensis L.) than annual ryegrass (Lolium multiflorum L.), but they provided as rapid initial cover. However, their persistence provides a means for bluegrass encroachment during the seedling year. Seedling competition was not due to any excretions from ryegrass seeds or seedlings. Turf quality of the improved perennials was superior to annual ryegrass, but slightly lower than pure bluegrass, because of frayed leaf tips. Redtop (Agrostis alba L.) and creeping red fescue (Festuca rubra L.) were less competitive to bluegrass than the ryegrasses, but they provided little advantage in ground cover; however, turf quality was similar to pure bluegrass. It was concluded that mixtures should be designed to obtain designated populations of companion and other seedlings that are needed for sufficient initial cover. The 5% PLS in this study was higher than normally recommended on a weight basis; therefore there was no advantage from higher seeding rates. Fall seeded mixtures generally contained the most Kentucky bluegrass, and the summer seedings had the least. Low clipping reduced competition from companion grasses, especially the improved perennial ryegrasses, which allowed a uniform transition toward bluegrass dominance with turf of average quality. Sod strength was best for the pure bluegrass turf, but root development of the improved perennial ryegrasses was best. / Master of Science