A phase II open and parallel reactogenicity, immunogenicity and safety trivalent meningitis vaccine (Mencevax) trial was conducted on 413 volunteer 2-29-year-old rural residents in Ethiopia in November/December 2005. Adverse events (AE) were monitored at 1h, 1, 2, 3, 7 and 28 days after vaccination. No serious AE occurred except for burn injury (one) and severe malaria (one) after day 28. Irritability (45/411), loss of appetite (27/411), pain at injection site (26/412), dizziness (18/409), crying (14/411), insomnia, headache and diarrhoea (13/411) were the most frequent AEs. Overall, the vaccine is safe in the age groups studied.