Background
Based on data available, Iran is located in a low risk area for multiple sclerosis (MS). The objective of the current study is to determine the age and sex adjusted prevalence and incidence of MS in southeastern Iran.

Methods
This cross-sectional case register study was conducted from January to August 2010. Considering that MS affects people aged between 16 and 50 years, we intended to find the incidence and prevalence of MS during this age range. Since all cases in this area are referred to our university hospital for confirmation of diagnosis, misdiagnosis is rare. Population data, based on the censuses carried out in 1996 and 2006, were obtained from the Iranian Bureau of Statistics to determine the number of people at risk.

Results
Totally 206 patients were identified according to the McDonald criteria. In 2009 the age-adjusted prevalence and incidence rates of MS for 16–50 year-old adults were 13.96 and 2.67 per 100,000 persons, respectively. Based on those values; the female to male ratio was 2.18. Between 2006 and 2009, the incidence rates increased 2.4 and 2.7 times in women and men, respectively. In 2009, the prevalence rates among the age ranges of <15, 16–35, 36–50 and =51 years were 1.44, 14.34, 12.24 and 1.45 per 100,000 persons, respectively, and the relapsing-remitting type of MS was the most prevalent form (65.8%).

Conclusion
According to the Kurtzke geographical distribution, the authors conclude that the prevalence of MS in southeastern Iran is in the intermediate range, and the incidence rate is showing a faster growth rate, compared to previous years.