Objective: We aimed to investigate the relationship between climate changes and the most commonly diagnosed three diseases according to ICD-10 coding registry of Ataturk University Hospital, located in Erzurum city center. Material and Methods: Between January 1 and December 31, 2009, 913 108 patients applied to Ataturk University Hospital outpatient clinics (including applications to the emergency unit). Data of 601 184 cases (65.8%) with an age range of 18-110 years were included in the study. The most common three diagnoses according to the ICD-10 codes were selected. These were "Other chest pain (R07.3)", "Headache (R51)", and "Pain in joint (M25.5)". Analyses were done to investigate the relationship between daily number of diagnoses and the studied meteorological values. Results: Mean age was 46.6 +/- 17.6 years. Yearly averages of temperature, dew point, humidity, and atmospheric pressure were 5.50 +/- 9.56 degrees C(-28-22), -0.48 +/- 7.30 degrees C (-31-12), 69.27 +/- 15.0% (31-98)and 1017.28 +/- 4.81 hPa (1000-1033), respectively. Pearson correlation analysis showed a significant positive correlation between M25.5 and temperature (r= 0.364, p< 0.001), dew point (r= 0.330, p<0.001), and atmospheric pressure (r= 0.140, p= 0.007) and a significant negative correlation between M25.5 and humidity (r= -0.234, p<0.001). There was no significant correlation between R07.3 as well as R51 and the meteorological variables (p> 0.05). In a linear regression analysis, temperature and atmospheric pressure were found as significant independent variables affecting number of daily admissions with M25.5. Conclusion: Meteorological variables affect daily admissions to hospital outpatient clinics with a diagnosis of "Pain in joint - M25.5". Contrary to classical knowledge, daily number of admissions due to "Pain in. joint" has a negative correlation with humidity and has a positive correlation with atmospheric pressure.