Newly publicized trial data are showing that hydroxyurea has strong anti-HIV activity, especially when combined with ddI, which has led to the opening of new trials testing the hydroxyurea/ddI combination. Hydroxyurea's purported mechanism of action against HIV is to inhibit a cellular enzyme, ribonucleotide reductase, that is essential for creating the special nucleotide units needed to form DNA. With fewer natural DNA nucleotides present, HIV's reverse transcriptase enzyme may be more likely to incorporate nucleoside analog compounds, such as AZT or ddI, into the DNA it is creating from HIV's RNA gene template. These nucleoside analogs are defective versions of the natural building blocks and force the viral DNA chain under construction to terminate prematurely. Additional information from various studies and new trials opening in the U.S. and abroad are provided.