Previous work has suggested that anxiety disorders are common in patients with Parkinson's disease. To study the relationship between anxiety and response fluctuations in Parkinson's patients further, we compared changes in Spielberger anxiety state scores with changes in parkinsonian disability as determined by the Parkinson's symptom diary (PSD). Anxiety state and PSD scores were obtained in 19 patients with idiopathic Parkinson's disease during on and off periods. Spielberger anxiety state scores were higher during off periods than during on periods (38.8 +/- 12.4 vs. 45.6 +/- 12.4, p < 0.03); further, the magnitude of the change in anxiety state scores was correlated with the change in PSD scores (rs = 0.616, p = 0.006). Spielberger anxiety trait scores were also correlated with disease duration. Our findings support existing data suggesting that anxiety can contribute significantly to morbidity in Parkinson's disease and suggest that anxiety varies with fluctuations in motor performance.