This paper, presented at a colloquium on memory systems, reviews recent studies on memory in humans and nonhuman primates. It highlights three key findings: (1) nondeclarative memory can be studied in various tasks involving classification learning, perceptuomotor skill, artificial grammar, and prototype abstraction; (2) cortical areas adjacent to the hippocampal formation, including entorhinal, perirhinal, and parahippocampal cortices, are essential for declarative memory; and (3) bilateral damage to the hippocampal formation in humans causes severe anterograde amnesia and temporally graded retrograde amnesia. The paper discusses two main topics: the distinction between declarative and nondeclarative memory systems, and the structures in the medial temporal lobe important for declarative memory. Declarative memory involves conscious recollection of facts and events, while nondeclarative memory involves unconscious learning and performance. Amnesic patients, who have bilateral damage to medial temporal lobe structures, perform well on tasks assessing nondeclarative memory but poorly on tasks assessing declarative memory. Studies in monkeys and humans show that the medial temporal lobe memory system, including the hippocampal formation and adjacent cortical areas, is essential for declarative memory. Damage to the hippocampal region causes significant memory impairment, while damage to the entorhinal cortex has less severe effects. The perirhinal cortex plays a critical role in visual memory, and the parahippocampal cortex is involved in spatial memory. In humans, bilateral damage to the hippocampal formation can cause severe anterograde and retrograde amnesia. Patients with such damage show varying degrees of memory impairment, with more extensive damage leading to more severe memory deficits. The findings suggest that different components of the medial temporal lobe memory system contribute uniquely to memory function. The paper concludes that the medial temporal lobe is essential for forming long-term declarative memory, while the neocortex serves as the permanent storage for memory. The study also highlights the importance of understanding the distinct roles of different brain structures in memory formation and retrieval.This paper, presented at a colloquium on memory systems, reviews recent studies on memory in humans and nonhuman primates. It highlights three key findings: (1) nondeclarative memory can be studied in various tasks involving classification learning, perceptuomotor skill, artificial grammar, and prototype abstraction; (2) cortical areas adjacent to the hippocampal formation, including entorhinal, perirhinal, and parahippocampal cortices, are essential for declarative memory; and (3) bilateral damage to the hippocampal formation in humans causes severe anterograde amnesia and temporally graded retrograde amnesia. The paper discusses two main topics: the distinction between declarative and nondeclarative memory systems, and the structures in the medial temporal lobe important for declarative memory. Declarative memory involves conscious recollection of facts and events, while nondeclarative memory involves unconscious learning and performance. Amnesic patients, who have bilateral damage to medial temporal lobe structures, perform well on tasks assessing nondeclarative memory but poorly on tasks assessing declarative memory. Studies in monkeys and humans show that the medial temporal lobe memory system, including the hippocampal formation and adjacent cortical areas, is essential for declarative memory. Damage to the hippocampal region causes significant memory impairment, while damage to the entorhinal cortex has less severe effects. The perirhinal cortex plays a critical role in visual memory, and the parahippocampal cortex is involved in spatial memory. In humans, bilateral damage to the hippocampal formation can cause severe anterograde and retrograde amnesia. Patients with such damage show varying degrees of memory impairment, with more extensive damage leading to more severe memory deficits. The findings suggest that different components of the medial temporal lobe memory system contribute uniquely to memory function. The paper concludes that the medial temporal lobe is essential for forming long-term declarative memory, while the neocortex serves as the permanent storage for memory. The study also highlights the importance of understanding the distinct roles of different brain structures in memory formation and retrieval.