Temperature, salinity and nutrient structure at a station, E1, in the English Channel 22 miles from Plymouth have been described for many individual years (see Armstrong & Butler, 1968, for example). By averaging the results gathered over many years (1903–61) the mean seasonal changes in the vertical distributions have been obtained (Pingree & Pennycuick, 1975). In this paper these distributions have been extended to incorporate data to 1975 and as well as presenting up-to-date mean distributions for temperature, salinity and inorganic phosphate, the mean distributions for silicate and nitrate are included. The purpose of the present work is to interpret the observed mean seasonal changes in the inorganic nutrient distributions in the light of recent measurements giving continuous variations of chemical properties (Armstrong & Lafond, 1966), and in particular, from the knowledge gained from continuous vertical chlorophyll ‘a’ determinations (Lorenzen, 1966; Holligan & Harbour, 1977; Pingree, Holligan & Head, 1977).