INTRODUCTION:Comparability and Quality Control in Cancer Registration remains an essential component of standardisation of cancer incidence data. The information provided by registries is used as a base-line data for cancer control and cancer research. As such misleading information will encourage fictious cancer patterns with over or under registration of some cancer sites. METHODOLOGY:The registration in Karachi started in 1995 and was confined to a single district of Karachi, the South District. Since 1998 the registration has extended to Karachi Division. For both the data sets, recommendations of the International Agency for Research on Cancer (IARC) and the International Association of Cancer Registries (IACR) have been followed to assure comparability and Quality Control of the results. RESULTS:The 2 data sets from Karachi show well-recorded demographic details of cases. Age was not a true indicator of validity in our case, as we have approximate ages of patients aggregated around quintiles and decades. All the cancer cases were reported from a minimum of 3 sources. Microscopic verifications (MV) were high. Cancers with the highest histological verification (HV) were those located in easily accessible sites e.g. breast, oral cavity and cervix. The age specific incidence rates (ASR) for Karachi South, all sites (1995-1999) was 148.1 males and 175.5 females. The same for Karachi Division (1998-99) was 132.4 males and 133.0 females. CONCLUSION:The cancer data in 1995 during the initial phase of registration was incomplete and suffered from inaccuracies associated with a lack of awareness in early years of registration. By the year 2001, the data (1995-1999) showed improved completion and accuracy. The incidence rates have shown no dramatic changes during the past 2 years. The malignancies also show a stable pattern, despite the possibility of under-registration of clinically diagnosed cases. The microscopic verification is high compared with the world region and similar to those observed in developed countries. This may be due to the widely available diagnostic facilities in Karachi and should therefore be considered an indicator of validity of registered data.