Intrinsic viscosities were determined at 25 degrees C for 10 samples of narrowly distributed sodium polystyrene sulfonate (the molecular weights M ranging from 0.9 to 1000 kg/mol) in pure water and in aqueous solutions containing 0.9 wt % NaCl from the slope of In eta(rel) versus polymer concentration. In the middle range of M, the [eta] values are in the former case almost 2 orders of magnitude larger than in the latter case. In the absence of salt, the plot of log [q] as a function of log M exhibits a sigmoidal shape, which can be approximated within the interval 3 < M (in kg mol(-1)) < 30 by log[eta] = -0.17 + 2.1 log M. In the presence of salt, the following relation holds true in the entire regime: log[eta] = -0. 13 + 0.86 log M. The concentration dependences of 'q of the present polyelectrolyte solutions and of solutions of uncharged polymers in organic solvents taken from the literature can be modeled quantitatively by means of recently reported relations at least up to reduced polymer concentration c[eta] = 5. The physical meaning of the parameters obtained from this modeling is surveyed.