A National Cancer Registry [NCR] has been established in Saudi Arabia 1994, as a population based incidence registry. Two reports have been published, the second one was in 1996 showing that the crude incidence rate [CIR] of cancer account for 39.1/100.000. To utilize the data of the registry, and employ it to determine the guidelines of the national cancer control program it was necessary to assess the quality of data in the registry. The measures of quality control were applied in King Khaled University Hospital [KKUH] to the data collected during January 1st to December 30th ,2000.The completeness of case ascertainment was assessed through utilization of multiple data sources; medical records, Pathology reports and death certificates, by employing capture recapture method and building up several log linear models. Validity of data by reabstracting random sample [10%] of records to assess minor and major disagreement of certain items and Timeliness of data through calculation of Reporting Delay Time [RDT]. A total of 991 cancer cases were reported to the registry during the study period, [71.4%] of them have Medical records, [77.5%] have Pathology reports and [28.1%] have death certificate. A total of 571 missed cases were identified from the overlapping sources of reporting and fitting log linear models which assured dependency of the reporting methods. The adjusted rate of ascertainment was [63.4%]. The stage of cancer showed the highest of major disagreement [43.6%] followed by the histology and primary site[25.6% and 10.3% respectively] and date of diagnosis accounts for [23.1%]. On the other hand, 250 cases showed RDT less than 6 months. The overall audit of The National Cancer Registry office in King Khaled University Hospital is reasonable for a beginning registry and several recommendations have to be executed to increase the the ascertainment of cases and minimize under-reporting, measure to improve accuracy of data should be built- in and incorporated in every step of the registration process. The time lag between diagnosis or admission and reporting to the registry office should be scheduled and strictly applied to ensure timely data and subsequent correct rates.