During the years 1988 to 1995, all diagnostic and therapeutic activities in the Breast Clinic, Ullevål Hospital, Oslo, Norway were registered prospectively. This paper presents the results from the registration. Of 4,436 new referrals, 1,169 had infiltrating mammary carcinoma and 63 ductal carcinoma in situ. 13.6% of those with breast carcinoma and 12.3% of those with benign breast disease had a first degree relative with breast cancer. The use of diagnostic biopsies for palpable and nonpalpable lesions decreased significantly through the period, from 155/112 in 1988 to 65/78 in 1995. For palpable lesions, the malign/benign ratio decreased from 0.82 in 1988 to 0.54 in 1995 while it improved from 0.43 to 0.88 for marked biopsies for nonpalpable lesions. Excluding those with mammographically and/or cytologically suspicious lesions from those who had a biopsy for a palpable lesion, we found that only seven out of 101 had cancer (ratio 0.07). Radical surgery was done in 790 cases with cytology as the only pre- and peroperative cancer verification. Three of them had a false positive cytology, as cancer was not found in the breast. One patient had metastasis later confirming that a cancer had been present; thus we had two false positive cytologies (2.5 per thousand). More than six axillary lymph nodes have to be examined in order to avoid false negative axillary status. In 1988 we had 41% with less than six nodes examined. This improved to 15% in 1995. Breast preserving therapy increased throughout the period from 4.1% in 1988 to 29.4% in 1995. Tumor size (pTI around 40%) and node positivity (35%) was fairly constant. In our opinion, a continuous prospective registration of the activity in a breast diagnostic centre is essential in order to improve and maintain service quality. The decision made by the Norwegian parliament in 1998 to introduce nation-wide mammography screening may be used to institute such continuous prospective registrations in all centres involved in the screening.