This paper makes a contribution to the study of Environmental Health. This study was done to establish a relation between the ozone levels in Mexicali and residents with cardiovascular diseases (CVD) who attended community clinics (CC's) from 1999 to 2000, which were closed to Enviromental Stations (ES). It was analyzed data of environmental ozone levels and the frecuency of visits of CVD patients to CC's in Mexicali from 1997 to 1998. It was detected that the ozone levels were incremented and so did, the quantity of visits to CC's. The ozone levels and the visited CC's were determined and so a statistical correlation was made. The hypothesis was based on previous epidemiological and toxicology findings and stated that the exposure to high and low levels of ozone (O3), either for short and long terms can cause Cardiovascular Diseases (CVD) to residents of Mexicali. This study was perfomed on 80 individuals; both, males and females. 40 of them were determinated to be in healthy conditions and other 40 persons were diagnosed to have cardiovascular diseases. Both groups were examined physically in different days (their cardiac rate, blood pressure and arterial oxygen saturation), then this clinical data was correlated with the ozone levels monitored by ES near of this CC's. It was learned that high ozone levels with or without winds ground-surface, at a superficial level is due to elevation of solar global radiation, and to temperature variations, along with excessive city traffic. For this purpose we made up a model to predict the ozone levels based on the solar radiation and on the temperature in Mexicali and this led to make up a database of CVD in each CC's. The data was collected daily, weekly, monthly during each season from 1999 to 2000. The ozone levels readings were obtained from ES located in strategic places in the city. The information of CVD patients was obtained from four community clinics near the ES. The heart diseases that were analyzed were: high blood pressure (HBP), squeamish heart disease (SHD) and cardiac arrhythmia. The values of the determination coefficient were higher than 0.7, and the results of the F Test indicated that the exposure to ozone could be related in at least 70% of CVD in locals.