In a prospective longitudinal study over several years, 58 patients with breast cancer are compared to 52 patients with fibrocystic disease and 24 patients with mastodynia. Results of coping (as assessed with the Bernese Coping Modes) are presented for the illness course of the first 6 months: (1) There is considerable variation of coping depending on illness situation and illness state. A core group of coping modes is predominant in most situations: 'attention & care', 'problem analysis', and 'Tackling'. In average 10 different coping modes were used by patients per given illness situation. (2) The different aspects of illness (in the same organ) ask for different coping. In the initial evaluation phase, however, the possibly fatal diagnosis overrides these differences. (3) Change over time (first 6 months) is net. Besides the core group of coping modes mentioned above, there is more variability in coping; in cancer a trend from a more fighting to a more accepting attitude is obvious; in fibrocystic disease more restricted coping is observed. Interdependence of coping with emotional stability and social adaptation will be studied as well.