The governing equations of Nesss analysis of the turbulent boundary layer with air injection have been solved by means of a digital computer. The results of the calculations are presented for various free-stream and local conditions. The results of Nesss analysis for air injection are compared with experimental data, and agreement is seen to be poor. A comparison of Nesss theory with incompressible velocity profile data provides a possible explanation for the discrepancy. A comparison of Nesss analysis for helium injection and experimental data shows good agreement for zero to moderate injection rates, and poor agreement for high injection rates. Therefore, it is concluded that for the general case of a turbulent boundary layer with mass addition, extreme caution should be employed when applying Nesss analysis.