Investigations into feeding behaviour and activity patterns, basically by biconical trap sampling, were carried out as part of a study of the population ecology and dynamics of Glossina pallidipes Austen in the Lambwe Valley, Kenya. Host-preference determinations from blood-meal analyses showed that over 80% of feeds constantly derived from bushbuck, buffalo and bushpig, in roughly equal proportions. Activity cycles in relation to feeding and pregnancy, investigated by mark-release-recapture and physiological methods, indicated four-day feeding intervals for males and three-day ones for females. The periodicity was more variable in males, and in females was contingent upon reproductive events, with feeding mainly taking place just before the in-utero moult of the second-instar larva to the third instar, just after larviposition and again at a more variable time during pregnancy. Comparisons of nutritional status from size, weight, and fat and haematin levels showed that flies from thicket had consistently greater fat reserves than flies from Acacia woodland and conifer plantation. No seasonal differences were found, nor any relationships between other variables. Based on hourly sample data, both sexes showed unimodal diel activity patterns, but with clear differences. Activity was most closely correlated with temperature, to a lesser extent with saturation deficit and least with light intensity, and better correlations were obtained with females than males. Diel activity patterns in both sexes were also age-related, and from the close similarity found between male and virgin female activity patterns it was inferred that male activity around traps was partly sexually oriented. Using electric screens in conjunction with biconical traps, comparisons between flies attracted to traps and those actually caught showed that traps were relatively more efficient in catching males than females, but captures were representative of the active population in terms of age and pregnancy.