Complete sets of quadratic and cubic force constants calculated for four isotopomers of dioxirane (CH2OO) are used to estimate vibration-rotation interaction contributions to observed values of rotational constants (B "), thereby yielding empirical estimates of the corresponding equilibrium values (B-e), At the highest levels of theory, least-squares refinements of atomic coordinates to both the empirical B-e values and the associated isotope shifts yield consistent sets of structural parameters. Recommended values are r(e)(CO)=1.3846+/-0.0005 Angstrom; r(e)(OO)=1.5133+/-0.0005 Angstrom; r(e)(CH)=1.0853+/-0.0015 Angstrom and theta(e)(HCH)=117.03+/-0.20 degrees. Semidiagonal quartic force constants (in the normal coordinate representation) also calculated for CH2OO are used to estimate anharmonic contributions to the fundamental vibrational frequencies. Arguments based on the latter set of results support those made in a previous theoretical study and clearly show that two infrared features assigned to dioxirane in a matrix-isolation experiment must be due to a different carrier.