Chemical parameters were monitored for 20 months in two shallow lakes near Barrow, Alaska. After formation of an ice cover, all parameters, except dissolved oxygen and pH, increased to a maximum at time of maximum ice depth. The pH values were essentially the inverse of other parameters after an ice cover was formed. Dissolved oxygen increased to supersaturation values in January and then gradually decreased until photosynthetic rates became significant. The lakes did not become anaerobic at any time. During and immediately after thawing, dissolved oxygen was near saturation and all other solutes (except pH) fell to minimum values. After this low point, concentrations began to increase toward another maximum in the following year. Solutes may be concentrated up to about 30 times by the thick ice cover. Ratios of solutes deviated widely from mean world values, probably because of the close proximity of the lakes to the ocean. Imikpuk, nearer to the ocean, had most ratios closer to ocean values. Seasonally, except at the time of the thaw, ratios were essentially constant except for Cl/HCO3. CJ/HCO3 decreased after ice formation and until photosynthetic rates became significant. During ice melt, ratios differed from values at other times, possibly because of differential occlusion of solutes in ice. INTRODUCTION Previous papers in this series have reported on algae, phytoplankton and primary productivity of Alaskan tundra lakes (Prescott, 1953, 1963a, 1963b; Prescott and Vinyard, 1965; Howard and Prescott, 1971). While studying the above elements of the eco,system, chemical parameters were also monitored. This paper reports on the seasonal variation of certain chemical parameters in tundra lakes near Barrow, Alaska. Other studies that have reported on chemical analyses of Alaskan tundra waters are Boyd (1959), Brown et al. (1962), Livingstone (1963), Lamar (1966), Holmquist (1967) and Kalif (1968). METHODS Two lakes near Barrow, Alaska, were studied for 20 months (September 1959-April 1961). These lakes, Imikpuk and Ikroavik, were described in an earlier paper (Howard and Prescott, 1971), but a few essential characteristics should be presented here. Both have about the same maximum depth (ca. 2-3 m) and neither freezes solid in the winter. Furthermore, Imikpuk is 100 m from the ocean while Ikroavik is 8 km inland. Samples were collected with a brass Kenmmerer bottle from the surface or immediately under the ice at intervals of about 2 weeks. The samples were conveyed to the laboratory in plastic bottles where