Results are presented of a program concerned with the development of tunable semi conductor diode lasers and their potential application toward solving some of the air pollution monitoring problems. The tunable diode lasers developed under the program are described. Information is given concerning some of the spectroscopic information obtained form the laser scans of portions of the gamma 1 band of SO2 between 1100 and 1200/cm, with special attention to comparison between experiment and theory. Initial experiments confirming the theory for remoter heterodyne detection are described. Next, experiments are discussed which relate to potential monitoring applications. The use of the first and second derivative techniques in point-sampling applications is compared, and an experiment showing present limits of detectability is described. Preliminary studies of interference effects, temperature and long-path transmission of diode radiation are also included.