A simple and rapid liquid chromatographic assay method using a fluorescence detector for quantitation of dihydroergotamine in plasma without extraction was developed. After precipitating the protein with acetonitrile, the supernatant liquid was directly injected for analysis. Chromatographic separation was achieved on C18reversed phase column and the mobile phase was the isocratic mixture of methanol, acetonitrile and glycine buffer (0.5:3.5:6.0). With this eluting solvent the drug and its internal standard were well separated from the interference of the plasma sample. The average recovery of dihydroergotamine from 6 replicate samples of different concentrations (5-30 ng/ml) were 92.2 ± 3.37%. The minimum amount of dihydroergotamine detectable by this method was 2 ng/ml of sample.