A programmed —1 ribosomal frameshift enables the human immunode-ficiency virus of type 1 (HIV-1) to produce its enzymes in a precise proportion relative to its structural proteins, which is necessary to control viral assembly and maturation. Here, we critically review models that account for this phenomenon, focusing on the most recent model, which postulates that the frameshift is triggered by an incomplete translocation and involves the slippage of three tRNAs. The effect of changes in the rate of translation initiation and elongation and the possible involvement of cellular factors in frameshifting are briefly examined. Finally, we highlight recent efforts intended to interfere with this type of frameshift as a strategy to develop novel anti-HIV drugs.