Background It is thought that mast seeding is a rare reproductive strategy in the tropics since tropical climates are less variable and fruit consumers tend to be more generalist in these regions. However previous tests of this hypothesis were based on only few tropical datasets and none from tropical South America. Moreover reproductive strategies have been quantified based on the coefficient of variation of interannual seed production an index that potentially confounds masting and high interannual variability in seed production. Methodology/Principal Findings We developed a new approach to model the monthly variability in seed production for 28 tree species and 20 liana species monitored during 5 years in a tropical forest of Central French Guiana. We found that 23% of the species showed a masting pattern 54% an annual fruiting pattern and 23% an irregular fruiting pattern. The majority of masting species were trees (8 out of 11) most of them animal-dispersed. The classification into reproductive strategies based on the coefficient of variation was inconsistent with our results in nearly half of the cases. Conclusions/Significance Our study is the first to clearly evidence the frequency of the masting strategy in a tropical forest community of Eastern South America. The commonness of the masting strategy in tropical plants may promote species coexistence through storage dynamics.