This review deals with the discussion of various hydrodynamic and heat-transfer characteristics of bubble and slurry bubble columns both for baffled and unbaffled configurations. The hydrodynamic properties include consideration of initial-bubble diameter, bubble growth, bubble size and size distribution, bubble velocity, gas-phase holdup, specific gas-liquid interfacial area, mass-transfer coefficients, different fluid-flow regimes, and effects of operating temperature, pressure, solids concentration, particle size and size range. Different correlations developed for estimating these gas-phase parameters are discussed and assessed. Comparatively less work has been performed on internally baffled bubble columns and therefore this is given detailed consideration in view of its practical importance. For predicting the gas-phase holdup, the drift-flux theory is examined and correlations are proposed for the terminal velocity of a swarm of bubbles in two- and three-phase dispersions both for baffled- and unbaffled-bubble columns. The hydrodynamic behavior of bubble columns in terms of a two-bubble class model development is presented in a historical perspective and is assessed for its ability to predict gas-phase holdup for two-phase systems involving liquids of low and high viscosities. This concept is found to be only moderately successful. Heat transfer from surfaces internal to bubble columns is discussed and experimental data of different investigators is assessed in relation to unbaffled- and baffled-bubble columns including both two- and three-phase systems. Parametric dependencies of the heat-transfer coefficient on different operating and system variables are established and employed to judge the available correlations. Various theoretical expressions developed for the heat-transfer coefficient in analogy to the surface renewal theory of mass transfer by Higbie, and involving the assumption of isotropic turbulence by Kolmogoroff, are critically examined and extended for baffled-bubble columns. A concept of similarly baffled-bubble columns is proposed and successfully tested for gas-phase holdup and heat-transfer coefficient for two- and three-phase systems simulating a wide range of viscosity values for the liquid and slurry phases. It has a very favorable impact on the design and scale-up of large bubble-column units. General conclusions possible on the basis of this detailed study are specifically listed and gaps of knowledge that currently exist are identified as areas for future investigation.