A number of paraneoplastic neurological syndromes have been described in association with small cell lung carcinoma and, less commonly, with other malignancies. We describe here the case of a 58-year-old woman with paraneoplastic limbic encephalitis (PLE) complicating squamous cell carcinoma of the lung.She presented with subacute cognitive decline, particularly memory loss, personality change and hallucinations. She had a history of ischaemic heart disease and an undifferentiated connective tissue disorder. Apart from a low titre of anti-nuclear antibody, all blood and CSF tests were normal, including inflammatory markers. CT scans of the brain demonstrated multiple low-density lesions in the cortex and cerebellum, but MRI of the brain only demonstrated lesions in the right frontal lobe and the right occipital lobe which did not have the appearance of metastases. Trans-oesophageal echocardiography, carotid doppler ultrasonography and a 24-hour tape all failed to identify any source of embolus. EEG demonstrated bilateral fronto-temporal changes.Subsequently a suspicious right upper lobe lesion on chest radiography was confirmed on CT, and bronchoscopy revealed a second right lower lobe endobronchial mass; biopsy confirmed squamous cell carcinoma.Early recognition of paraneoplastic syndromes like PLE should result in prompt diagnosis and treatment of these cancers.