Department of Physical Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Calcutta.-700 032 Manuscript received 14 May 1980, revised 14 July 1981, accepted 26 February 1982 Polyethylene (PE), though insoluble in all solvents near room temperature, has been found to be soluble in a number of binary mixtures, one of which is CS2. \(\eta_{sp}/c\) vs c plots for such systems have been found to be consistently of negative slope and in a few cases, this negative slope at low dilution is so pronounced as to appear like the 'upswing', typical of polyelectrolytes. The Mark-Houwink constants in a few such cosolvent pairs have been determined at a number of temperatures. Besides, the intrinsic viscosity-molecular weight relationship deduced theoretically by Palit has also been tested and found to be satisfactory. Further,. the viscometric data have been utilised to calculate the unperturbed dimensions of PE (at different temperatures) by the use of Stockmayer-Fixman equation which agrees well with literature data. However, the viscosity data do not comply with the expectation of the theories of Kurata-Stockmayer-Roig or Flory-Schaefgen or Ptitsyn which may be due to a difference in composition of the solution layer and the bulk of the solution.