Fresh fruits are susceptible of be attacked by several pathogenic fungi after harvest due to both their high water and nutrients content and their loss of most of the intrinsic resistance that protected them over their development while attached to the plant. Most rot pathogens can be controlled by various methods such as refrigeration, controlled atmospheres and fungicides. Biological control strategies are emerging as promising alternatives to the use of synthetic fungicides. Several factors must be considered for the selection of biocontrol agents to be used against postharvest fruits diseases. Survivability of the antagonist is a major factor to determine its usefulness. Antagonists must survive and be effective after their exposure to both postharvest treatments and storage conditions. Several antagonistic microorganisms have been found that can effectively inhibit postharvest diseases. Just as there is a diversity among microorganisms, there is also a diversity of mechanisms by which they operate. Although in most cases these mechanisms have not been satisfactorily elucidated, they are likely to involve antibiosis, nutrient competition, stimulation of host defense, predation and parasitism. In many cases, probably more than one mechanism operate. The marketing of some of these antagonists may be feasible and they could be an alternative to synthetic pesticides.