There is great potential for establishing historical records of water temperature / the oxygen isotopic composition of sea water (0180 - H20) and the carbon isotopic composition of dissolved inorganic carbon (o13C - LC02) from oxygen and carbon isotopic records in scallop shell calcite (0180 and o13C)_ Variations in o13C - LC02in oceanic environments often reflect productivity cycles which may potentially be recorded within shell o13C records. The establishment of such records is based upon two fundamental assumptions_ These are that precipitation of shell calcite occurs in isotopic equilibrium with sea water and that growth occurs over an entire annual cycle_ Important information may also be gained from microgrowth patterns on the scallop shell surface ('striae') once factors governing their deposition are understood_ The above assumptions were tested for the scallop (Pecten maximus) by controlled experiment and in a year - long field study_ During periods of slow growth shell oxygen isotopes were found to be precipitated in isotopic equilibrium with sea water_ Shell carbon isotopes were found to be depleted with respect to isotopic equilibrium_ This was interpreted as resulting from a metabolic effect, probably reflecting incorporation of respiratory CO2 into the growing shell. At higher shell growth rates depletions / further depletions in 0180 / 013C with respect to isotopic equilibrium occurred, interpreted as reflecting kinetic effects_ Shell growth exhibited distinct seasonality, with growth cessation during the Winter months (below 8-9°C) and maximal growth rates in the Summer_ Stria deposition was found to be strongly related to shell growth rate_ The combined effects of growth cessation and precipitation of shell isotopes out of isotopic equilibrium with sea water precluded accurate determination of mean and annual ranges of water temperature / 0180 -H20 and o13C -LC02 from the shell isotopic record_ Shell 0180 / o13C and striae abundance records for Pecten maximus collected from an offshore site were interpreted in the context of the calibration work undertaken_