The coil-globule transition behaviour of poly(methyl methacrylate) has been studied in isoamyl acetate by using the dynamic light scattering technique. The dimensions of the polymer show smooth and continuous contraction below a temperature (61.0 degrees C). The hydrodynamic size of PMMA in isoamyl acetate (M-w = 3.3 x 10(6) g mol(-1)) decreases to 41% in an unperturbed state at 18.4 degrees C. The temperature dependence of a chain contraction can be represented by a master curve in alpha(h)(3) \ tau \ M-w(1/2) vs \ tau \ M-w(1/2) plot, where alpha(h) = R-h/R-h,R-theta and tau = (T - theta)/theta. A high-chain density value implies that the highly collapsed globule contains 56% isoamyl acetate in its hydrodynamic volume. (C) 1999 Elsevier Science Ltd. All rights reserved.