In this review, the biosynthesis, catabolism, ecological significance, and modes of action of purine alkaloids particularly, caffeine, theobromine and theophylline in plants are discussed. In the biosynthesis of caffeine, progress has been made in enzymology, the amino acid sequence of the enzymes, and in the genes encoding N-methyltransferases. In addition, caffeine-deficient plants have been produced. The ecology of purine alkaloids has not proved to be particularly promising. However, advances have been made in insecticidal and allelopathic fields, and in the role of microorganisms play in the changes that these compounds undergo in the soil. Caffeine inhibits cell plate formation during telophase throughout the development of coffee plants and other species.