The use of highly sensitive procedures for detecting human chorionic gonadotropin (hCG) has brought about an increasing occurrence of test results that are difficult to interpret. Furthermore, different results on the same serum sample can be obtained by different methods of measurement and, in extreme cases, serum hCG may be positive by one method and negative by the other. These observations are important, since patients may be hospitalized and receive unnecessary treatment as a result of confusing laboratory data. The clinical significance of slightly elevated serum hCG level is reviewed.