The demand for new antibiotics increased due to the misuse and over use of antibiotics inrnvarious sectors creating an evolutionary pressure and resulting in multi drug resistant strainsrnwhich result in increment of morbidity and mortality in the world. The main objective of thisrnstudy was to explore the potential of alkaliphilic actinomycetes isolated from three Ethiopianrnsoda lakes. About 171 isolates were screened for antibiotic production using cell free culturernsupernatant taken from the submerged fermentation and ethyl acetate crude extract of thernculture, of which 93.6% of them showed antibiotic activity with cell free culture supernatant andrn76 % of them with crude ethyl acetate extract against the test microorganisms used. Based onrnbroad spectrum activity, zone of inhibition obtained and their activity with the use of crude ethylrnacetate extract, two isolates LCHACT17and LABACT21 were chosen for furtherrncharacterization. Antibiotic production was favored when phosphate concentrations was 0.2 %rnfor LCHACT 17 and for LABACT 21. Yeast extract and sodium nitrate (for LCHACT 17) andrncombination of casein and potassium nitrate (for LABACT 21) were suitable nitrogen sources forrnantibiotic production. From the carbon sources used soluble starch was the best carbon sourcernfor antibiotic production by LCHACT17 while sucrose was found to be preferred carbon sourcernby LABACT 21. Similarly it was observed that 1% sodium chloride concentration was favorablernfor antibiotic production by both isolates and the pH parameter indicated that pH10 (forrnLABACT 21) and pH11 (for LCHACT17) were the optimum pH for antibiotic production. Therncell free culture supernatant of both isolates was stable at alkaline pH and decreases in activityrnat lower pH (pH 6 and below). The cell free culture supernatant of LCHACT17 was stable up torn60oc while LABACT 21 was stable up to 40 oc. The minimum inhibitory concentration (MIC) ofrnLCHACT17 crude ethyl acetate extract against Streptococcus pneumonia was 12.5 mg/ml.rnKey words/ phrases: Alkaliphiles, Antibiotics, Disk diffusion.