A measles outbreak occurred in the Kirinyaga District in February, 1985. Immunization coverage against measles was above 80% in the district and increased by age. The immunization against measles was lowest (46%) in the age group (8-11) months and highest (90%) in the (36-59) months age group. However, the overall vaccine effectiveness in the childhood population (8-59) months was only 43.5% and peaked (91.5%) in the (24-35) months age group. Based on these and similar findings in some developed and developing countries the proposal for global measles eradication is suggestively premature and particularly so for the tropics. The eradication of measles poses far more substantial obstacles than did smallpox eradication. That transmission continues to occur in communities with very high measles vaccination coverage and high vaccine effectiveness (vaccine efficacy) is a true testimony to the difficulty involved.