This article updates the 1990 Annual Review of Neuroscience article on the human brain's attention system. The original framework proposed three networks: alerting, orienting, and executive. Over the past 20 years, research has expanded on these networks, adding two new networks and refining the understanding of their interactions. The alerting network involves brain stem and right hemisphere systems related to arousal and vigilance. The orienting network includes parietal and frontal areas involved in directing attention to sensory input. The executive network involves midline frontal and anterior cingulate cortex, responsible for cognitive control and conflict resolution. Recent studies have shown that these networks are involved in various cognitive functions, including attention, emotion, and decision-making. The alerting network is associated with the release of norepinephrine, while the orienting network is linked to cholinergic systems. The executive network is involved in maintaining attention and resolving conflicts. Research has also shown that individual differences in attention network efficiency are influenced by genetic and environmental factors. The article also discusses the development of attention systems from infancy to adulthood, highlighting the role of the orienting network in early development and the increasing involvement of the executive network as children grow. It emphasizes the importance of understanding these networks for developing interventions for attention-related disorders. The study of attention networks has led to a better understanding of both normal and pathological processes, and future research may further refine our understanding of these systems.This article updates the 1990 Annual Review of Neuroscience article on the human brain's attention system. The original framework proposed three networks: alerting, orienting, and executive. Over the past 20 years, research has expanded on these networks, adding two new networks and refining the understanding of their interactions. The alerting network involves brain stem and right hemisphere systems related to arousal and vigilance. The orienting network includes parietal and frontal areas involved in directing attention to sensory input. The executive network involves midline frontal and anterior cingulate cortex, responsible for cognitive control and conflict resolution. Recent studies have shown that these networks are involved in various cognitive functions, including attention, emotion, and decision-making. The alerting network is associated with the release of norepinephrine, while the orienting network is linked to cholinergic systems. The executive network is involved in maintaining attention and resolving conflicts. Research has also shown that individual differences in attention network efficiency are influenced by genetic and environmental factors. The article also discusses the development of attention systems from infancy to adulthood, highlighting the role of the orienting network in early development and the increasing involvement of the executive network as children grow. It emphasizes the importance of understanding these networks for developing interventions for attention-related disorders. The study of attention networks has led to a better understanding of both normal and pathological processes, and future research may further refine our understanding of these systems.