Zinc is generally recognized to be an essential micronutrient for the growth and development of both plants and animals., thus there is a priori evidence for its occurrence in all natural waters which support living organisms. The zinc in lakes may be divided into two fractions, that present in liquid phases such as the open waters and that present in or on solid materials such as the seston and the bottom sediments. In the liquid phases this element may be present as a hydrated ion, a complexed ion, or associated with soluble organic compounds. In the solid phases zinc may form part of an inorganic precipitate, occupy a space in the crystal lattice structure of clays, be held as an exchangeable ion by either organic or inorganic exchange complexes, or be present in living organisms as a functional component of the metabolic systems. The zinc cycle may be thought of as the flux of zinc between the different phases superimposed upon the movements of the phases themselves. For example, both the uptake of a zinc ion from solution by a clay particle and the movement of that particle as it settles to become a part of the bottom sediments would be included. It is the purpose of this study to consider the first part of this cycle, namely the distribution of zinc between various liquid and solid phases of lakes and some of the factors which affect this distribution. Specific consideration will be given to planktonic algae, organic detritus, bottom sediments, natural lake seston, and a limited number of aquatic animals. This information will be utilized to deduce a general outline of the freshwater zinc cycle.