Abstract: Results of a two-year study on the waste waters of a textile mill near Nanjangad, Mysore, Karnataka, reveal that effluents have objectionable amounts of total suspended solids and BOD, COD, oils and grease, lead, zinc as per ISI standards. Physico and chemical factors that have been correlated with the algae growing in the polluted area. Seasional variations in the algal flora of the effluent stream have been studied. Algae as the index organisms of pollution are discussed.