Air-blast atomization of viscous non-Newtonian liquids was carried out using a co-axial twin-fluid atomizer. Both Newtonian and non-Newtonian liquids were investigated with particular emphasis on the non-Newtonian theological characteristics. Shear thinning, extension thinning and extension thickening fluids were investigated. Non-Newtonian shear viscosities were measured over five decades of shear rates gamma for 12 solutions of polymeric materials. By using the die-swell technique, the first normal stress difference N-1 was determined for all solutions. The contraction flow technique was also used for measurement of the extensional viscosity. It was found that viscoelastic liquids are much more difficult to atomize than viscoinelastic liquids. The normal stresses developed in viscoelastic materials are much higher than their associated shear stresses. Consequently, the development of the large normal stresses appears to be the most important theological mechanism that inhibits breakup. The accuracy of the wave-mechanism-based models in predicting droplet sizes after breakup of inelastic non-Newtonian liquids has also been demonstrated. The atomized drop sizes were expressed in terms of three dimensionless groups, the liquid/air mass ratio (M(1)/M(A)), the Weber number (We) and the Ohnesorge number (Z) in simple forms whose exponents and coefficients were determined by least-squares fit to the experimental data. The exponents of the power dependences of the wave-mechanism-based simple models were found to be comparable to their counterparts reported in the literature for air-blast atomization of Newtonian liquids with viscosities up to 1 Pa s. For shear thinning viscoinelastic materials it was found that the atomization quality is closely related to the apparent viscosity of the fluid in the limit of infinite shear rates (eta(infinity)) The functional dependence of the Sauter mean diameter (SMD) on eta(infinity) is: SMD proportional to eta(infinity)(0.42).