Hospital visitor-companions are being used as a source of controls in an ongoing case-control study on breast cancer in the Philippines. As a tool for rapid epidemiologic assessment in obtaining research data for case-control studies, visitor-companions may serve as an alternative source of controls. To determine their generalizability and consistency, this proposed group was compared to neighbourhood controls and to hospital-patient controls. Hospital visitor-companions were comparable to neighbourhood controls in terms of cooperation in the interviews, height, weight, marital status, longest residence, education, cigarette smoking, alcohol intake, annual income, proportion with salaried jobs, ownership of house, land, and business, number of people living in the house, number of siblings, medical history, parity, menopausal status, breast feeding practices, and use of oral contraceptives. Neighbourhood controls however had longer interview durations than visitor-companion controls (p less than 0.05). Hospital-patient controls were less likely to breast feed, had lower alcohol intake, and had more exposure to chronic diseases and diagnostic x-ray than visitor-companion or neighbourhood controls (p less than 0.05). It was concluded that visitor-companions may usefully serve as an alternative source of controls for case-control studies when their limitations are taken into consideration during analysis.