This paper describes the compressive creep behaviour of an equimolar titanium nitride (TiN) -titanium diboride (TiB2) particulate composite material in the temperature range 900-1200 degreesC and the stress range 100 to 200 MPa. Attention was devoted to the specific role of the atmosphere in influencing the creep mechanism : air and impure argon were tested. In both atmospheres, the creep tests conducted during 24 hours exhibited primary and dominant secondary steady-state stages but did not show a tertiary stage. The stress exponent in air is 1.3 and the apparent activation energies are 140 and 160 kJ/mol, respectively, in air and argon. To understand the part played by oxidation, thermogravimetric analyses have been conducted in static air between 1000 and 1200 degreesC. A reaction process is observed in this temperature range (Ea = 170 kJ/mol).