Recent measured values of the thermal conductivity of nitrogen are represented (140–348 C) over a range of pressure (400 atm) and also for argon for the same temperature range and a pressure of 140 atm. The conductivities have been reduced for “zero” pressure and the effect of pressure evaluated as (λp – λ0) or Δλ. The pressure effects are represented by the form Δλ = a1(p/T) + an(p/T)n. An exhaustive comparison of earlier data has not been carried out since the main objective at this time was to report our recent observations. However, most of the recent λ0 data have been formulated and compared in Table 1 (N2) and Table 5 (A). The equations for (N2) and (A) which are believed most satisfactory are the “ensemble” equations for λ0 following: (N2)λ0·103=2.433T1/21+208.8τ/1012τ(Watts/MC)(A)λ0·103=1.557T1/21+170.5τ/108τ(Watts/MC) The Δλ equations suggested are the following: (N2)Δλ=(λp−λ0)=13.56(p/T)+1.39(p/T)2P.Johannin(700C:1200atm)(N2)Δλ=(λp−λ0)=13.19(p/T)+3.35(p/T)3KeyesandVines(347C:400atm)(A)Δλ=(λp−λ0)=10.13(p/T)+5.99(p/T)2KeyesandVines(347C:140atm)