Hyperfine structure in the S324 ground state of the radioactive atom As76 has been investigated by the method of magnetic resonance in an atomic beam produced by microwave discharge dissociation of arsenic vapor. ΔF=0 resonances were observed within both the F=52 and F=72 atomic levels at several values of magnetic field up to about 5 oe, indicating that the spin of the As76 nucleus is 2. An analysis of multiple quantum transition spectra within the same F states gave a measurement for two of the hfs intervals: Δν72,52=±(117±4) Mc/sec and Δν52,32=±(69±16) Mc/sec, with the same sign for both. From the value of the hfs constant A, the magnitude of the magnetic field at the arsenic nucleus is (1.33±0.15)×105 oe in reasonable agreement with the variation in this field among similar atoms. The value of gJ has been found to be 1.994±0.003 for arsenic. © 1961 The American Physical Society.