Zinc sulphide ore was leached in columns of various heights and under various irrigation rates. Sphalerite and pyrite bioleaching kinetics agreed with the colonization shrinking core model where an initial colonization phase was followed by a steady rate phase. Columns irrigated at the same rate showed colonization rate constants (μ) of both sphalerite and pyrite that increased linearly with the inverse of column height. Similarly, the shrinking core rate constants (k) were also inversely proportional to heap height. When the irrigation rate was physically adjusted to compensate for height, columns ranging from 1 m to 8 m tall showed leaching curves that were identical. In essence, sphalerite and pyrite heap bioleaching kinetics were proportional to the irrigation rate divided by the height (L/h). The relationships governing the colonization and shrinking core rate constants were different for sphalerite and pyrite. Sphalerite bioleaching was favoured over pyrite at lower values of L/h. The degree of sulphur oxidation was favoured at higher values of L/h. © 2005 Elsevier Ltd. All rights reserved.