A cross-flow air-water cooling tower is not counter-current although performance calculations are usually performed using counter-current flow humidification theory, on the understanding that this is an acceptable approximation. A two-dimensional numerical analysis of a cross-flow tower has been undertaken to compare the results with the counter-flow case. For typical installations, the two are in acceptable agreement, though differences become larger for high performance situations. The model allows the effect of water and air flow maldistribution to be estimated.