The density of a gas (ρ) is mass per unit volume (ρ = m/V). According to the ideal gas law, PV = nRT, volume (V) is affected by both pressure (P) and temperature (T). Since density is inversely proportional to volume (ρ ∝ 1/V), any change in pressure or temperature will alter the volume and thus the density. Therefore, gas density depends on both pressure and temperature.

Final answer: pressure and temperature