New strategies emerge targeting cell functions manipulated by viruses to replicate. Murine Leukemia virus is an excellent manipulator of cellular functions because it has minimal coding capacity with only 3 genes common to all retroviruses (gag, pol, env). In contrast, HIV-1 (the agent responsible for AIDS) is more complex with several additional viral proteins directly regulating viral RNA metabolism. Nevertheless, these two retroviruses perform the same replication cycle, in which translation is a key step. To study viral translation in cells we are combining SunTag and MS2-RNA imaging strategies. For visualization at a single-molecule level, several copies of the SunTag epitopes were fused to the nascent Gag protein. Then, a fluorescent antibody binds to the SunTag and amplifies the signal. The colocalization of SunTag and MS2 signals provides information on the ratio of translated/untranslated viral RNA, translation localization, and kinetics. First, we studied fixed-cells, and images were acquired in a widefield fluorescent microscope and the colocalization between nascent peptide and RNA dots was detected using Imaris. We have derived all the molecular tools for the study of the translation of these two viruses. Interesting preliminary results show about 20% of MLV and 35% of HIV RNA are translated at the same time.