Nonpolymeric phosphonates are well-known scale inhibitors in the upstream oil and gas industry because they afford several advantages over other classes of inhibitors. But few of these phosphonates show good environmental properties as well as good thermal stability for high-temperature squeeze applications. Given the known high seawater biodegradability of benzoic acid, we have synthesized and tested several easily accessible monoaromatic phosphonates. The tests include dynamic tube-blocking experiments for both calcite and barite scaling, thermal stability, calcium compatibility, and seawater biodegradation according to the OECD 306 protocol. The new aromatic inhibitors were compared to known aminophosphonate scale inhibitors including the aromatic amino acid derivative, phenylalanine diaminomethylenediphosphonate. The results indicate that improved performance can be obtained together with good thermal stability for the phenolic derivatives, but too much aromatic ring substitutions lead to lower biodegradation.