This case control study investigated environmental factors in 74 confirmed cases of meningococcal disease (MD). In children aged under 5, passive smoking in the home (30 or more cigarettes daily) was associated with an odds ratio (OR) of 7.5 (95% confidence interval (CI) 1.46–38.66). ORs increased both with the numbers of cigarettes smoked and with the number of smokers in the household, suggesting a dose–response relationship. MD in this age group was also significantly associated with household overcrowding (more than 1.5 persons per room) (OR 6.0, 95% CI 1.10–32.8), with kisses on the mouth with 4 or more contacts in the previous 2 weeks (OR 2.46, 95% CI 1.09–5.56), with exposure to dust from plaster, brick or stone in the previous 2 weeks (OR 2.24, 95% CI 1.07–4.65); and with changes in residence (OR 3.0, 95% CI 1.0–8.99), marital arguments (OR 3.0, 95 % CI 1.26–7.17) and legal disputes in the previous 6 months (OR 3.10, 95% CI 1.24–7.78). These associations were independent of social class. Public health measures to lower the prevalence of cigarette smoking by parents of young children may reduce the incidence of MD. The influence of building dust and stressful life events merits further investigation.