The book "Indolic Metabolism and Melatonin Synthesis in the Pineal Gland" offers a comprehensive analysis of the complex processes involved in melatonin synthesis in the pineal gland. It highlights the role of melatonin synthesis in the circadian rhythm and examines the interactions between serotonin and melatonin. The authors, Jesús M. Míguez, Manuel A. Aldegunde, and Lucinda Paz Valiñas, present results from various experiments aimed at clarifying the metabolic and functional relationships between these two indoles. The book also addresses the modulatory role of extracellular serotonin in melatonin synthesis and the application of microdialysis techniques for the quantitative analysis of rhythmic melatonin release in the pineal gland of rats. This detailed investigation is of great interest to professionals and students in the life sciences who are studying the mechanisms of the circadian system and neurotransmission.