The growth of two blue-green algae species Anabaena wisconsinense and Spirulina platensis under outdoor conditions (Egyptian conditions) was studied; variation in chemical composition of algal cells due to season of cultivation was also investigated. Average cell mass productivity reached the maximum in summer followed by autumn and spring in both  Anabaena  and  Spirulina  The decline in crude protein with ageing of culture was accompanied by an increase in fat and total carbohydrates contents and by the decrease of nucleic acid and mineral contents. Amino acid analysis showed that both species were deficient in methionine. Methods of drying significantly affected amino acid composition.  Growth and chemical composition of Spirulina cells are maximum crude protein content was around 63% for all seasons. This was attained at the age of 12 days for spring and summer and at 18 days in autumn seasons, the calculated average and maximum productivity of algal cells and crude protein showed the highest value in summer culture followed by autumn and spring seasons.  Summer temperature naturally ranged higher than the other two seasons and consequently, resulted in higher growth rate and protein productivity. However, analysis of variance comparing algal growth rate and yields of spring, summer and autumn cultures were not significant.