This investigation pertains to nucleate boiling in a thin film on a horizontal tube at atmospheric and subatmospheric pressures. The experiments are carried out with distilled water and sodium chloride solutions (35 000 and 50 000 p.p.m.) in the pressure range 60-100 kN m-2. An enhancement in the nucleate boiling heat transfer coefficient is noted for boiling in the horizontal tube falling film. A correlation is proposed to predict the boiling heat transfer coefficient for distilled water and sodium chloride solution in a thin film on a horizontal stainless steel tube at atmospheric and subatmospheric pressures. © 1989.