Tremor is commonly the first neurologic sign of Parkinson's disease (PD) that leads patients to see a physician. Knowing how to differentiate the resting tremor of PD from essential tremor is an important diagnostic skill. Unlike patients with essential tremor, those with PD have other neurologic findings. A diagnosis of PD is likely if the patient has two of three major clinical features: resting tremor, bradykinesia, and rigidity. Minor signs may also be seen, including cognitive slowing, speech abnormalities, depression, dysautonomia, and sleep disturbances. The history and physical exam can determine if the patient has parkinsonism and whether the cause is Parkinson's disease.