A sensitive assay based on the polymerase chain reaction (PCR) has been developed to detect sugarcane bacilliform badnavirus (SCBV) in diseased sugarcane plants. Two sets of primer pairs, which prime the synthesis of DNA from the putative aspartic protease and reverse transcriptase coding regions, were evaluated. Best results were obtained with the primer pair SCBVF5 and SCBVR5, which primes the synthesis of a 221-bp virus-specific fragment from total nucleic acid extracts of diseased sugarcane plants. The viral origin of the PCR products was confirmed by Southern hybridization with a 1,602-bp fragment from the cloned SCBV genome. This diagnostic test was used to detect SCBV infection of noble canes (Saccharum officinarum), commercial hybrids, clones within the ''Saccharum complex'' including S. robustum, S. spontaneum, S. barberi, Erianthus arundinaceus, and E. ravennae, as well as banana infected with banana streak virus. This sensitive screening test has been used to show that SCBV is widely distributed throughout Saccharum and related germ plasm.