Pneumatic reactors have been widely employed in various sectors of the chemical industry, especially where it required high heat and mass transfer rates. This study aimed to obtain correlations that allow the prediction of global gas hold-up (epsilon(G)) and volumetric oxygen transfer coefficient (k(L)a), and compare these values, for three models of pneumatic reactors on two scales utilizing viscous Newtonian fluids. Values of k(L)a were obtained using the dynamic pressure-step method, while for EG was used a new proposed of measure. Comparing the three models of reactors studied, it was observed that the mass transfer was superior to draft-tube airlift of 10 L working volume. All correlations showed good fit to the experimental data, and comparisons with correlations from the literature demonstrate the need for further similar studies due to shortage of data available, mainly for airlift reactors operated with viscous Newtonian fluids. The proposed correlations in the present study allow prediction of the main mass transfer parameters and thus contribute significantly for project, operation, and scale-up of bioprocesses involving high density cell cultures of Newtonian characteristic. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier BM. All rights reserved.