In this paper we report a patient with Parkinson's disease (PD) presenting with subacute motor symptoms, especially rigidity. The 75-year-old man had relatively moderate PD for 12 years, which was treated with levodopa until he developed marked rigidity. The rigidity became worse, with prolonged off-periods, despite treatment with increased doses of levodopa. At the time of hospitalization he was unable to walk independently, but the clinical neurological examination only revealed aggravation of parkinsonian signs. MRI of the brain showed an intracerebral lesion, which was later confirmed as glioblastoma multiforme. The main feature was onset of marked rigidity a few weeks before severe tumour-specific symptoms developed, but spasticity or hyperreflexia were neither reported at the time of symptom exacerbation nor during hospitalization. This case demonstrates the importance of considering other underlying neurological disease in parkinsonian patients presenting with rapid progression of parkinsonian symptoms.