Several new 4-diazopyrazole derivatives were prepared by the reaction of 3-methyl-5 (substituted-benzamido) pyrazoles with an excess of nitrous acid in acetic acid solution. The compounds were tested for antiretroviral activity in HIV-1 infected MT-4 cells and antiproliferative effects against a panel of human leukemia, lymphoma and solid tumor cell lines. They were also tested for activity against representative gram-negative (Shigella, ...