A broad band X- , gamma-ray spectral study of the Seyfert 2 galaxy NGC 7172 is presented . We use our ASCA observations from May 1995 and combine these with the CGRO OSSE data from March 1995 . The only Seyfert 2 galaxy previously to have been modelled over such a broad spectral range is NGC 4945 . The ASCA GIS data alone , can be acceptably described by a model consisting of a power law , with a photon index \Gamma = 1.58 \pm 0.12 , affected by absorption due to intervening neutral matter along the line of sight , with an equivalent hydrogen column density N _ { H } = ( 8.2 ^ { +0.6 } _ { -0.5 } ) \times 10 ^ { 22 } cm ^ { -2 } . An Fe K \alpha emission line is not required by the fits . The observed flux in the 2 - 10 keV range is F _ { 2 - 10 } = ( 4.75 \pm 0.09 ) \times 10 ^ { -11 } erg cm ^ { -2 } s ^ { -1 } , which corresponds to a small increase since the Ginga measurement in October 1989 . The power law found is flatter than what is expected in the unified model of Seyfert galaxies . Combining these ASCA data with the CGRO OSSE data from March 1995 , the above conclusions do not change . In this case , we also find that the most probable model for the data is an absorbed power law , but being affected by a high energy exponential cut-off . The power law is still flat with \Gamma = 1.54 \pm 0.13 , while N _ { H } = ( 8.1 \pm 0.6 ) \times 10 ^ { 22 } cm ^ { -2 } . The OSSE data do not contradict the flat spectrum found from using the ASCA data alone , which could have been an artifact of the narrow spectral range covered by this single instrument . Even though it is not possible to completely reject an alternative explanation to the observed flat spectrum in terms of a transmission or a reflection model , the spectral index of the underlying power law of NGC 7172 appears actually to have varied from 1.85 to 1.5 since the Ginga observations in 1989 . The e-folding energy is relatively well constrained and lies at 140 ^ { +310 } _ { -70 } keV , using the CGRO OSSE viewing period with the highest quality data . We note , however , that the CGRO OSSE spectral shape appears to be variable on a time scale of weeks .