The beta decay of the radioactive members of the mass-eight and -twelve triads has been studied with a spiral-orbit spectrometer having a 1.3% resolution. The end point, half-life and log-ft values respectively are: for N{sup 12}, 16.37 {+-} 0.06 MeV, 11.43 {+-} 0.05 milliseconds, and 4.17; for B{sup 12}, 13.40 {+-} 0.05 MeV, 20.6 {+-} 0.2 msec and 4.11; for B{sup 8}, 14 MeV (broad), 0.75 {+-} 0.02 sec, and 5.72; and for Li{sup 8}, 13 Mev (broad), 0.87 {+-} 0.01 sec, and 5.67. The mass excesses in millimass units are: for N{sup 12}, 22.48 {+-} 0.06; for B{sup 12}, 18.19 {+-} 0.06; for B{sup 8}, 27.08 {+-} 0.13; and for Li{sup 8}, 24.97 {+-} 0.09. The shapes of the Kurie function for the mirror pairs indicate positron and electron transitions to the same levels of the daughter nuclide, with greater percentages in the positron branches relative to the ground-state transitions because of the higher energy available. The Li{sup 8} and B{sup 8} shapes are consistent with the shape of the alpha spectrum following the decay of the Be{sup 8} daughter. Less than 1% of the Li{sup 8} transition and less than 5% of the B{sup 8} transition go to …