The demand for health and medical care is analysed within a generalised Grossman-type health investment model. Its underlying assumptions are shown to differ from those employed earlier in a manner which avoids some of the criticisms levelled at Grossman's model. The comparative static predictions of the generalised model are examined; and it is demonstrated that most previous health investment models are derivable from it. Also, the present model is applicable to a new, wider range of problems thus increasing the scope of economic explanations of health behaviour.