Recently, Gitchel et al.1 reported that “pervasive ocular tremor” is present in patients with Parkinson's disease (PD) while they attempt steady visual fixation. This was a universal finding in the 112 PD patients that they studied, but was generally absent from their 60 healthy control subjects. This finding of a pervasive ocular tremor in PD has generated substantial interest but also controversy, as is evident by the article by Kaski et al.,2 and the ensuing correspondence by Baron et al.3. Because pervasive ocular tremor might provide a most useful biomarker for PD, it seems justified to examine the validity of the measurements of Gitchel et al.1 and consider alternative explanations for their results, before they gain wide acceptance and application. Here we summarize some of the evidence for and against the case for pervasive ocular tremor in PD, and suggest future experiments to resolve conflicting opinions.