Cyanobacterium Spirulina is in ever increasing demand internationally due to its high value bio-chemical constituents which find application in areas like health foods and therapeutics, especially for its high protein content. The Spirulina protein is superior to practically all proteins including those from legumes, and is comparable to milk proteins for that matter. Moreover, interest in its phycocyanin, b-carotene, polyunsaturated acids (PUFA) and super oxide dismutase (SOD) contents has attracted the attention of researchers the world over towards protecting, promoting and preserving the production of this useful micro-organism. The present investigation deals with examining the impact of various physical stresses viz. intensity and photo-period of light, varying chromatic regimes, temperature, pH, etc., on the growth of Spirulina platensis-S5 to spell the appropriate conditions for raising the strain in laboratory. No earlier report of this kind is available, so far, to our knowledge. The experimental results suggested that 16 : 8 hours light : dark regime at light intensity of 2000 +/- 200 lux, temperature of 30 +/- 1 degrees C and pH of 9.1 are the optimal growth conditions for the test micro-organisim. The growth under different chromatic regimes observed the order yellow> red> green> blue.