This thesis deals with a series of mass balance studies carried out on two glaciers in north-west Spitsbergen, Midre Lovenbreen and Austre Broggerbreen, using an energy balance model. A general description of glaciers, including their classification and the manner in which their surfaces may be sub-divided, is carried out. A discussion is then made concerning the processes which affect the mass balance of a glacier surface, and the techniques used, both field and computational, to determine this parameter. The first modelling exercises carried out were to determine how sensitive the model used is to perturbations in various climatic parameters. This project had a number of objectives: 1) determining what difference is made by applying simplified meteorological data instead of measured data, 2) modelling the mass balances of Midre Lovenbreen and Austre Broggerbreen to reproduce the values obtained by field surveys, 3) modelling the mass balances of these glaciers to determine the effect changes representing future warmer, and past cooler, climates would have on their balance behaviour. It was found that temperature was the parameter the model results were most sensitive to, and cloud height the least. There is a difference in the final results depending upon what meteorological data form is used, simplified or measured. The mass balances of the glaciers could be best reproduced by a model version that included an altitudinal precipitation correction expression and excluded the latent heat component of the energy equation. A rise in temperature of 4 to 50c will result in most of the glacier's present extent becoming areas of negative balance, despite applying a 50% increase in precipitation, while a decrease in temperature of 2 to 30c will considerably increase the area which will experience a positive balance, sometimes to lower than the glaciers' present lowest point.