The coil-globule transition was studied for poly(methyl methacrylate) (PMMA) in acetonitrile with molecular weights M-w = 6.4 x 10(6) and 11.4 x 10(6) by static light scattering. Because of the Very slow phase separation, the mean-square radius of gyration was determined reliably in the temperature range from above the Theta temperature at 44.0 degreesC down to 5 degreesC. PMMA chains in acetonitrile collapsed slowly to equilibrium globules, and the collapse processes were measured for time periods of 30 min to 7 days depending the molecular weight and temperature. The behavior of the equilibrium expansion factor was represented as a function of (1 - Theta/T)M-1/2 and compared with the theoretical predictions by Birshtein and Pryamitsyn and those by Grosberg and Kuznetsov. The second and third virial coefficients for segment interactions were estimated from the observed coil-globule transition curve by using the theories and were comparable with literature values due to the second and third virial coefficients of the dilute solution.