Data mining along with soft computing techniques helps to unravel hidden relationships and diagnose diseases efficiently even with uncertainties and inaccuracies. Coronary Heart Disease (CHD) is a killer disease leading to heart attack and sudden deaths. Since the diagnosis involves vague symptoms and tedious procedures, diagnosis is usually time-consuming and false diagnosis may occur. A fuzzy system is one of the soft computing methodologies is proposed in this paper along with a data mining technique for efficient diagnosis of coronary heart disease. Though the database has 76 attributes, only 14 attributes are found to be efficient for CHD diagnosis as per all the published experiments and doctors' opinion. So only the essential attributes are taken from the heart disease database. From these attributes crisp rules are obtained by employing CART decision tree algorithm, which are then applied to the fuzzy system. A Particle Swarm Optimization (PSO) technique is applied for the optimization of the fuzzy membership functions where the parameters of the membership functions are altered to new positions. The result interpreted from the fuzzy system predicts the prevalence of coronary heart disease and also the system's accuracy was found to be good.