Objectives: to determine by a systematic review the proportion of gingival squamous cell carcinoma (GSCC) in relation to all oral squamous cell carcinomas (OSCC).Material and methods: Two independent reviewers searched the Medline database for relevant English language publications. Studies were selected if they met the following criteria: case series of histologically confirmed OSCC, excluding extraoral and vermilion border of lip carcinomas. Recorded data for each study: total number of patients with OSCC, number of patients with GSCC, which included alveolar ridge and retromolar area occurrences and excluded other unspecified oral sites. Other recorded data were age, gender, relative exposures to tobacco, alcohol, betel nut, and occurrence of oral lichen planus or other putative risk factors. Results: the search yielded a list of 118 publications, of which 33 were selected and 4 were included. The total number of patients with OSCC, in the 4 studies, was 2167. The proportion of patients with GSCC was: 36.5 % in the Indian study, 28% and 25% in the two US studies, and 10,9 % in the Italian. Data from the Indian and the US studies indicated that men are less affected by GSCC than women (proportions: 27.8 % vs 31.7 %, odds ratio 0.81, 95 % confidence interval: 0.67-0.99). Conclusions: GSCC proportions were highly variable. To establish if such differences are due to methodological flaws or to ethnic, geographic or cultural factors, further appropriate investigations are required. Keywords: gingiva, squamous cell carcinoma, epidemiology, systematic review