The study examines differences in consumption and economic behaviour among male and female heroin users. A sample of heroin injectors (n = 1834) was interviewed near the needle-exchange service in Oslo and information on consumption, prices, and income was recorded. The consumption pattern of the heroin addicts varies by gender, with females consuming relatively less alcohol and cannabis but significantly more heroin than their male counterparts. The finding of greater heroin consumption among women is surprising. By means of a switching regression model, price and income elasticities for heroin are estimated. Women appear to be more responsive than men to changes in prices. However, the elasticities also differ substantially by dealing status, and non-dealers are more price-responsive than dealers. Non-dealing males emerge with a higher income elasticity compared with their female counterparts, whereas female dealers seem to respond more to changes in income than do male dealers.