The essential principles of coke making are summarized with emphasis on the complex balances within the main phases that determine coke qualities. Correlations of coal properties with coke properties, and their significance for blending are noted. Emphasis is placed on the conduct of coking tests rather than measuring coal properties, and on the disparities between various coke properties. Coking in a full width test coke oven is considered essential to sound decision making on blend adjustments.