Vapor pressures of high boiling pollutants are extremely low under ambient conditions; these data are, however, required with reasonable accuracy for better understanding and predicting the transport and fate of pollutants in the environment. Direct measurements of vapor pressures below 1 kPa are complicated and subject to systematic errors; it is therefore more suitable for combine experimental data at higher pressures with the related thermal data (heats of phase transition, heat capacities) available in the low pressure range. Such an extrapolation of vapor pressures controlled by exact thermodynamic relationships yields consistent data describing the vapor-liquid or vapor-solid saturation line under environmental conditions. The method has been used to generate recommended vapor pressures between 223.15 and 323.15 K for 20 alkylbenzenes with normal boiling temperatures above 423 K. All available primary literature data characterizing the vapor-liquid saturation line have been evaluated and the selected values are correlated using the three parameter Cox equation. For those compounds that are solid at ambient temperatures the thermodynamic calculation of vapor pressures below the triple point temperature is also performed. The recommended data are tabulated at discrete temperatures and presented also as parameters of correlating equations.