Sensory and motor impairments can occur at multiple sites within the sensorimotor pathway with healthy ageing and after stroke. We do not fully understand the physiological mechanisms underpinning these changes or their interactions. This thesis investigated changes in the upper-limb sensorimotor pathway with age and post-stroke across multiple modalities of hand sensation and motor function. Age-appropriate data were derived for healthy subjects. After stroke cutaneous sensation and proprioception were studied as were changes in neural drive to the elbow flexor muscles. A final methodological study identified the optimal method to selectively activate a single muscle using electrical stimulation at the motor point. The first study found a complex pattern of reduced sensation that varied with age, hand, site and sex. The greatest changes on the palm rather than the fingertips. In the second study the pattern of motor function decline with age varied with modality and was more strongly linked to sensation on the palm than the fingers. The pattern of proprioception error after stroke was different at the elbow and wrist depending on the level of motor function. The magnitude of cutaneous sensory impairments were only evident after stratification according to sensory function. Peripheral and cortical stimulation assessments of voluntary activation suggested muscle weakness on the more-affected side was due to both reduced connectivity in the descending tracts and an inability to drive through those connections, whereas the less-affected side was not being optimally driven. Voluntary activation could not be assessed with cortical stimulation due to the inconsistency of the superimposed twitch. In the final study the location, size and muscle response of the motor point varied according to the method employed. This study emphasised the importance of not relying on anatomical landmarks or anthropometric proportions to identify neuromuscular structures. The principle findings of this thesis are that single tests or assessment sites are unlikely to adequately identify or explain changes in sensory or motor function. The results emphasise the complex pattern of age-related change in healthy people, and demonstrate that appropriate stratification for test modality was necessary to reveal the magnitude and incidence of reduced sensation after stroke.