We analyzed data from the National Health Insurance Research (NHIR) database in the year 2000 to estimate the seasonal variation in the chickenpox rate in Taiwan. All chickenpox cases listed in the NHIR database were included (n = 165,719). A Lorenz curve was plotted and a chi-square test for equal proportions calculated for seasonal variation. To determine the effects of temperature and season on outcome values, generalized estimating equation methods were utilized to adjust the effects of other possible influencing factors and take into account the within-subject dependence over repeated assessments. All four regions of the country had highest incidence rates in January, and three of them had lowest rates in September. Incidence was significantly higher in females aged 15-24 years than in males. An increment of 1 degrees C resulted in an incidence ratio of approximately 0.98 or, equivalently, a 10 degrees C increment gives an incidence ratio of approximately 0.78. The results suggest that season and temperature are significantly related to the incidence of chickenpox. Infectious diseases can be monitored. Prevention procedures can be taken by understanding its pattern and activity in order to decide the best policy for vaccination. Further studies are warranted, particularly for long-term trends, and in other nations with different seasonal temperatures from Taiwan.