A case-control study of the home environment of 140 asthmatic children and 140 controls (matched for age, sex and socio-economic status) was carried out in two semi-urban Nigerian teaching hospitals. The mean age of the children was 66 months, and the mean monthly family income was US $50.00. The average number of people in a household was seven, with a mean sleeping density of 4.9 persons per sleeping area. There was a strong and significant association between asthma and a damp, mouldy bedroom (OR = 11.2, p < 0.001), household pets (OR = 116.8, p < 0.001), cigarette smoke (OR = 2.1, p < 0.01), mosquito coil (OR = 3.7, p < 0.001), and rodents/cockroaches (OR = 113.7, p < 0.001). There was a curious but unexplained protective effect of indoor biomass smoke (OR = 0.6, p < 0.001), indoor plants (OR = 0.5, p < 0.01), mould growth elsewhere in the home (OR = 0.5, p < 0.01), and cosmetic aerosols (OR = 0.6, p < 0.05). Control of the micro- as well as the macro-environment of the asthmatic child as an adjuvant to drug therapy is discussed.