A synthesis procedure for and characterization of a tetra-ortho-methyl substituted three-ringed cyanate ester monomer, 4,4'-[1,3-phenylenebis(1-methylethylidene)]bis[2,6-dimethyl]phenylcyanato, and the corresponding cured resin are described with comparative characterization of the resin analogue without the orthomethyl substitutents. The othro-methylation lowered the dielectric from 2.64 to 2.59 at 1 GHz and from 2.64 to 2.48 GHz at 15 GHz, whereas the tan delta was not significantly affected. Other physical properties also affected included a 40 degreesC decrease in the glass-transition temperature, an increase in the thermal-expansion coefficients, and a reduction in thermogravimetric stability.