Background
An unethical clinical study that entailed withholding treatment from women diagnosed with cervical intraepithelial neoplasia 3 (CIN3) was conducted at National Women’s Hospital, Auckland, New Zealand. Women with microinvasive carcinoma of the cervix also had treatment withheld.

Aims
To describe the management and outcomes for women with microinvasive carcinoma for many of whom conventional treatment was withheld.

Materials and Methods
Retrospective cohort study of women with a diagnosis of stage 1A cervical carcinoma at National Women’s Hospital. Medical records, cytology and histopathology were reviewed and data linked with cancer and death registries up to December 2000.

Results
Between 1955 and 1976, 62 women were initially diagnosed with stage 1A cervical cancer and 20 were diagnosed during follow up (to 1995). Sixty of the 82 women had initial management characterised as ‘probably non‐curative’; 20 of these received only a small diagnostic excision. Women in the latter group were more likely to: (i) subsequently have positive cytology (P < 0.0005), (ii) have untreated positive cytology (P = 0.02), and (iii) undergo multiple biopsies after initial management (P = 0.001). Of the women who received only a small diagnostic excision, eight of 20 developed invasive carcinoma of the cervix (≥ stage 1B) or vaginal vault, compared to two of 22 women who received initial treatment characterised as ‘probably curative’. Conclusions Women with microinvasive carcinoma were included in a natural history study of CIN3; they underwent numerous procedures designed to observe rather than treat their condition, and had a substantial risk of invasive cancer.