Objective To develop a method for simultaneous detection of DNA of CT,UU and NG in clinical specimens.Method A multiplex PCR and target specific oligonucleotides probes for hybridization in a microwell format with colorimetric detection was designed and compared with the routine PCR method.Results Laboratory tests showed that this method has a high specificity and sensitivity(0 1 fg).166 swab specimens collected from STD patients Luoyang in 1998 were derected.The positire rates of CT,UU and NG were 22.9%,54.8% and 34 3% respectively meanwhile,the co infection of two and three etiologic agents were 22 2% and 4 8% respectively.It is concordant with routine PCR method.Conclusion The results indicate that the multiplex PCR assay is a simple,rapid,specific and sensitive method for detection of the three etiologic agents simultaneously.