About 1-2% of women with gynaecological cancers are found to have two or more simultaneous independent primary malignancies. Low stage multiple primaries must be distinguished from metastasis from one to other site for correct management. Synchronous tumours in the ovary and endometrium are the commonest combination. Most of these can be accurately categorised by standard histological criteria. Molecular testing has been advocated for valuable adjunctive information in ambiguous cases but must be interpreted with clinicopathological correlation: loss of heterozygosity, pTEN or beta-catenin gene mutational analysis, microsatellite instability and most recently gene expression profiling have all been used. The pattern of beta-catenin immunohistochemical expression has been reported to be of value. A very low percentage of women with synchronous primaries in the uterus and ovary are HNPCC patients and testing for mismatch repair gene mutations is unnecessary in all cases, even if young; the diagnosis of HNPCC should be based on standard criteria. Women with endometrial cancer under 50 are more likely than older patients to have a synchronous ovarian cancer. Rarer combinations of synchronous tumours are less well studied but may also represent a mixture of unusual patterns of metastasis and multifocal origin; these are discussed briefly.