On April 2, 1974, a balloon-borne observation of the gamma-ray background at 4 mbar pressure was conducted in the energy band .3-12.27 MeV. The measurements were made at a geomagnetic cutoff rigidity of 11.9 GV. Cosmicray-induced activation of the Nal(Tl) detector was discovered to be a major source of the background count rate in the energy region .15-2.5 MeV. The cosmic diffuse gamma radiation makes a sizable contribution to the background count rate in the low energy region .3 - .15 MeV. At these energies lower limits for the diffuse gamma-ray flux were determined. A search of the detector data for evidence of cosmic gamma-ray bursts proved inconclusive. The conclusions drawn from the background study can be utilized in order to design a very low background gammaray detector for celestial observations.