INTRODUCTION & OBJECTIVES: Epidemiological studies suggest that environment plays an important role in the aetiology of cancer. Prostate cancer (CaP) in males and breast cancer in females have many similarities and this may include a shared role for dietary and/or environmental factors. Thus, if a cancer (e.g. CaP) arises in males, one could hypothesize that risk of another disease requiring the same initiating factor (e.g. breast cancer) in co-habiting partners might be elevated. MATERIAL & METHODS: We conducted an observational-questionnaire study in North-West England evaluating the medical histories of CaP males and their female partners. Details regarding previous partners (>10 y co-habitation) were also sought. Self-filled questionnaires were obtained from 548 males, 81 of whom provided information on previous female partners (PFPs) and 448 current female partners (CFPs). RESULTS: The key observations include • Among CaP males, 15% had another family member with a diagnosis of CaP. • Self-reported habits showed a highly-significant concordance for smoking status and alcohol consumption between male and female partners. • Cancers of the breast, colorectum and lung were commonly reported in females while colorectal and skin cancers were apparently high in CaP males. • Observed rates over a 30-y period (1971-2001) of common cancers (breast, colorectal or lung) in female partners and colorectal cancer in males were compared to the cumulative expected probability (estimated using crude incidence rates for England provided by the Office of National Statistics, UK) using a Chi-Square Goodness-of-Fit test. The differences in the proportions was significantly higher (p <001) in the observed rates of breast and lung cancers in PFPs; the observed rates of lung cancer were lower in CFPs (p <0.02). However, colorectal cancers in males and the rates for breast, colorectal or lung cancer among CFPs and the total female cohort (CFPs plus PFPs) did not show a statistically signifi cant difference from national estimates. • Cancer occurrence within broad bands (y) of co-habitation exhibited a tendency to increase in a time-related fashion; this was significant (p <0.05) for breast or lung cancers among PFPs. CONCLUSIONS: One would surmise that there exists a high concordance of shared dietary and lifestyle habits among the co-habiting partners. In this small pilot study we have observed that the rates of breast and lung cancers are higher than expected among PFPs of men who go on to develop CaP. Further investigations employing larger cohorts, a histological verification of reported cancers and genotype profi ling might assist in clarifying the role of shared lifestyles.