This paper deals with heat exchangers having plain fins on a staggered array of circular tubes. Correlations are developed to predict the air-side heat transfer coefficient and friction factor as a function of the Reynolds number and geometric variables of the heat exchanger. A multiple regression technique was used to correlate 47 sets of heat exchanger data to develop the heat transfer and friction correlations. The correlations are applicable to heat exchangers having small diameter tubes (or large tube pitch to tube diameter ratio), whose performance previous correlations failed to predict adequately. The heat transfer correlation applicable to three or more row configuration predicts 88 % of the data within ± 20 %. and the heat transfer coefficient applicable to one or two row configuration predicts 93 % of the data within ± 20 %. The friction correlation predicts 86 % of the data within ± 20 %.