By screening of a collection of 50 000 small-molecule compounds, we recently identified 4-arylazo-3,5-diamino-1H-pyrazoles as a novel group of anti-biofilm agents. Here, we report a SAR study based on 60 analogues by examining ways in which the pharmacophore can be further optimized, for example, via substitutions in the aryl ring. The SAR study revealed the very potent anti-biofilm compound 4-(2-(2-fluorophenyl)hydrazineylidene)-5-imino-4,5-dihydro-1H-pyrazol-3-amine (2). This journal is