PhOH was condensed with CH(2)O in aq. medium in presence of NaOH to resp. resins. The reaction was followed by detn. of conductance of the reaction mixt. and by detn. of concns. of unconverted substrates. The Box-Behnken exptl. design was used at changing PhOH/CH(2)O mole ratio (1.5-3.5), catalyst concn. (0.2-1 cg/g) and temp. (60-80 degrees C). The conductance after 10 and 210 min of the reaction was described by polynomial equations as functions of the PhOH/CH(2)O mole ratio and catalyst concn. The equations were successfully verified. The conductometric measurements were recommended for pract. following the reaction course under lab. and industrial conditions.