To study the clinical picture of lathyrism in Unnao, India and compare it with that reported from other endemic areas, 41 patients from Unnao were studied. Their mean age was 42.9 years (range 22-85) and the mean duration of the illness was 17.1 years (range 2-30). They had been regularly consuming Lathyrus Sativus (LS). The patients complained of walking difficulty due to weakness and leg stiffness (32 each), and of frequency of micturition (4). Gait abnormalities included spastic gait (24), toe walking (18) and the necessary use of walking sticks (13). Weakness was mild to moderate, and was less prominent than was spasticity. In 8 patients the physical signs were asymmetrical. Peripheral neuropathy was present in only one patient, but muscle atrophy and widespread fasciculations were not found. A higher frequency of peripheral neuropathy and lower motor neuron involvement has been reported from Bangladesh and Israel. Severe spasticity in the absence of prominent weakness in lathyrism may be due to the involvement of certain specific groups of corticospinal fibres.