The aim of this study was to assess the outcomes of women treated conservatively for a serous borderline ovarian tumour with stromal microinvasion (SBOT-SMI) but without micropapillary pattern. Ten women treated conservatively for a stage I (n= 8) or stage IIIB (n= 2) tumour were followed up. With a median follow-up duration of 62 months (range 7-117 months), five recurrences developed on the preserved ovary. All lesions were borderline recurrences (with noninvasive peritoneal implants in one). All women are currently disease free. Three women achieved a spontaneous pregnancy and three became pregnant after an in vitro fertilisation procedure. This study suggests that conservative treatment of SBOT-SMI is safe.