||Karnal bunt, is a disease of the wheat grain caused by a fungus and is said to have evolved in South Asia. It has come under concern in both India and Mexico over the last few years. In the present treatise, an attempt has been made to develop a disease prediction system, now that effective chemicals are available. Re-investigating the life cycle showed that the allentoid spores, the infective agent, multiplies and monkey jumps from leaf to leaf till they reach the boot leaf. It is hypothesised that spells of drizzle, at boot leaf sheath stage washes the spores into the emerging earhead and causes infection. Subsequently, if the mid March maximum temperatures are mild, the systemic movement of the pathogen gets enhanced. Such situations lead towards an epidemic. In other words, more rainy days at the time of earhead emergence favours the disease. Over a decade climatic and field data on KB from India was collected and similar information from Mexico were statistically analyzed following multiple regression, analysis ot variance and the t test ot siqnificance. For both Indian and Mexican situations linear models could be developed having a R2 value ot 0.9, which indicates their high fitness. The Mexican prediction system was validated tor 1990 and shows that the results agree with the prediction. The analysis indicate that it is the number of rainy days at boot leaf stage that is important in the recurrence of severe KB. These results support the hypothesis of inoculum rundown into the boot leaf sheath as the main mechanism favouring infection. As the accurate disease prediction model opens up new areas for research such as the boot leaf earhead charecters etc. There is a serious information gap on the epidemiology of the disease and hence a number of experiments have been suggested as a follow up on the present report.