Abstract: Objective To study whether a single s erum β-hCG determination in pregnancies ach ieved by assist ed reproductive technologies(ART) can accurately predict pregna ncy viability and inviable pregnancies, multiple gestation. Method Fo urty-nine consecutive succe ssful ART pregnancies between November 1998 and February 2000 were studied retrospectively. Fourty-six subjects had a serum β-hCG determinetion 14 day s after ET were analyzed. Results 36 of the 46(78.3%) were found to be viable. The mean β-hCG value of the nonviable was(89±24) U/L, the viable was(472±45)U/L，statistically significant differences were fou nd between thes e two groups, P＜0.05. According to the cut off v alue of a single β-hCG＞100 U/L in distinguishing viable from nonviable pregnancies achieved, the sensitivity was 97%, specificity 80%,the positive predictive value 95%,the negative p redictive value 89%. Ten of the 46 were multiple gestations, the mean β-hCG o f the multiple ge stations ［(656±70) U/L］ was significantly different from that o f the singleton pregnancies ［(288±20)U/L］.The probability of viable, and fu rthermore multiple p regnancies increase when the value of β-hCG goes up. Conclusion A single early serum β-hCG determinaton 14 alays after ET is clinically valuab le in predicting p regnancy outcome achieved by ART. It will help the gynecologists to take some m easurements in timely. Early reassuring tests may reduce an xiety of the couple.