1 Introductory Remarks.- 2 Plasticity in the Peripheral Somatosensory Nervous System.- 2.1 Aspects of Plasticity in the Peripheral Nervous System.- 2.2 Survival and Loss of Sensory Neurons After Lesions of the Peripheral Nervous System.- 2.3 Collateral Sprouting of Primary Afferent Fibres in the Periphery.- 2.4 Regeneration of Somatic Sensory Afferent Fibres.- 2.5 Modality Specificity of Somatosensory Nerve Regeneration.- 2.6 Major Conclusions.- 3 Plasticity and the Mystacial Vibrissae of Rodents.- 3.1 General Account of Pathway.- 3.2 Normal Development of the Vibrissae and Their Neural Connections to the Cerebral Cortex.- 3.3 Effects of Lesions and Manipulations in Prenatal, Neonatal and Developing Animals.- 3.4 Plasticity in the Vibrissa System of Adult Animals.- 3.5 Major Conclusions.- 4 Plasticity and the Spinal Dorsal Horn (with Notes on Homologous Regions of the Trigeminal Nuclei).- 4.1 Experimental Strategies for Demonstration of Plasticity in the Dorsal Horn of the Spinal Cord and Trigeminal Nuclei.- 4.2 Overview of Dorsal Horn Organization.- 4.3 Somatotopic Organization of the Dorsal Horn.- 4.4 Effect of Lesions on Somatotopic Organization.- 4.5 Mechanisms Underlying the Somatotopic Reorganization of Dorsal Horn Neurons.- 4.6 Plasticity of the Developing Dorsal Hor.- 4.7 Major Conclusions.- 5 Plasticity and the Dorsal Column Nuclei.- 5.1 Advantages of the Dorsal Column Nuclei for Studies of Plasticity.- 5.2 Organization of the Dorsal Column Nuclei.- 5.3 Alterations of Inputs to the Nuclei.- 5.4 Evidence for Ineffective Afferent Connections.- 5.5 Recovery from Sensorimotor Deficits Following Dorsal Column Lesions.- 5.6 Plasticity of the DCN During Development.- 5.7 Major Conclusions.- 6 Plasticity and the Somatosensory Thalamus.- 6.1 Experimental Strategies andPlasticity in the Ventral Posterior Nuclei of the Thalamus.- 6.2 Anatomical Organization of Inputs and Outputs of the Ventral Posterior Nuclei.- 6.3 Responses of Neurons to Cutaneous Stimulation and the Effects of Anaesthetics and Other Drugs.- 6.4 Somatotopic Organization of the VPL and VPM.- 6.5 Effects of Alteration of Input on Somatotopic Organization.- 6.6 Major Conclusions.- 7 Plasticity and the Somatosensory Cerebral Cortex.- 7.1 Experimental Strategies and Cortical Plasticity..- 7.2 Plasticity in the Cortex of Adult and Developing Primates.- 7.3 Plasticity in the Cortex of Adult and Developing Cats.- 7.4 Plasticity in the Cortex of Adult and Infant Raccoons.- 7.5 Plasticity in the Cortex of Adult and Developing Rodents.- 7.6 Major Conclusions.- 8 Concluding Remarks.- 8.1 Plasticity During Development.- 8.2 Evaluation of Experimentally Induced Plasticity in Adult Animals.- 8.3 The Case for Ineffective Connections.- 8.4 Spatial Extent of Immediate and Long-Term Changes in Somatotopic Organization.- 8.5 Normal Physiological Mechanisms and Plasticity.- 8.6 Role of Plasticity in the Mature Somatosensory System.- References.