2-Diazopropane and diazo compounds derived from aromatic aldehydes were reacted with aromatic esters of 3-hydroxyprop-1-yne to give the aromatic esters of 5-hydroxymethyl-3-substituted pyrazoles. Anti-microbial screening using the Gram positive ( Staphylococcus aureus and Enterococcus fecalis) and Gram negative ( Escherichia coli and Klebsiella pneumoniae) bacteria and the yeast Candida albicans, showed that these compounds had promising activity against both Gram positive and Gram negative bacteria.