For the period 1976 through 1996, we carried out an incidence and prevalence study of myasthenia gravis in the County of the Coast and Gorski kotar, Croatia. This was the first epidemiological study of myasthenia gravis in Croatia. A total of 43 incident cases were identified. Overall the average crude annual incidence rate was 6.52 per 1,000,000 person-years; 5.59 per 1,000,000 person-years for men and 7.41 per 1,000,000 person-years for women. The incidence rate was 6.30 (95% confidence intervals 4.56-8.51), age-adjusted to the European population and 5.17 (95% confidence intervals 3.74-6.98), age-adjusted to the world population. On 31 December 1996, there were 32 prevalent cases. The crude prevalence was 99 per 1,000,000 population (95% confidence intervals 67.7-139.6). The prevalence adjusted to the European and world populations was 101.9 (95% confidence intervals 69.7-143.7) and 75.9 (95% confidence intervals 51.9-107) per 1,000,000 population, respectively. Our incidence findings are similar to those reported in North-East Italy but lower than those in the United States. Our prevalence findings were generally higher than those in Northern European Countries but lower than those in the United States. Standardization of rates to the European or world population could facilitate comparison between different populations.