Clinically, multiple system atrophy is difficult to differentiate from other basal ganglia disorders such as idiopathic Parkinson's disease or other types of cerebellar ataxia. The "hot cross bun"sign is a radiological sign which, it has been claimed, is highly specific for multiple system atrophy, and we describe four cases in which this sign occurred. In one patient, multiple system atrophy was clinically diagnosed, but in the other three, the respective clinical diagnosis was spinocerebellar ataxia type 1, type 2 (genetically), and old cerebellar hemorrhage. We therefore suggest that the hot cross bun sign reflects degeneration of transverse pontocerebellar fibers and is not a pathognomic sign of multiple system atrophy.