A large-scale computer service is not always available in many countries with tuberculosis problems needing epidemiological analysis. To facilitate work in such countries, a simple epidemiological model was made to calculate annual trends in the prevalence and incidence of tuberculosis and its infection, in tuberculosis mortality and in BCG coverage, using average parameter values not specific for age groups or birth year cohorts. To test its approximation capabilities and limits, the model was applied to epidemiological data from Japan, where sufficient information was available from repeated nationwide sample surveys and national statistics. The approximation was satisfactory within certain limits. The model is best used with a desk-top computer, but the calculations can be performed with a small calculator or even by hand.