Sorghum crop provides excellent forage in dry land areas. It has ability to tolerate high temperature and grow under minimal soil moisture. Sugar content in Sorghum is of prime importance regarding, animal feed value as well as biofuel production. However, high level of HCN toxin production is a serious problem associated with this crop which could be lethal to animals if ingested in greater quantities. In this study hydrocyanic acid and sugar content dynamics were determined on two forage sorghum cultivars i.e. JS-2002 and Chakwal sorghum at different developmental stages (bootinga and 50% headingb). Fertilizer treatments of nitrogen (0, 60 and 120 kg ha-1) and sulphur levels (0, 20 and 40 kg ha-1) were applied in replicates. The experiment was arranged in randomized complete block design. The results clearly depicted that increase in nitrogen levels gradually increased the HCN and sugar contents irrespective to sulphur and delayed harvesting times. Increase in HCN (21a & 22b%) and brix value (56a & 59b%) was found more at 120 kg N ha-1 when compared with 0 kg N ha-1 (control) treatment. Similarly increase in sulphur application caused increase in brix value however; inverse relationship with HCN content was recorded. Results also indicated that sorghum cultivar JS-2002 produced 27a & 40b% decline in HCN content while 8a & 18b% more sugar content when compared with Chakwal sorghum. Seasonal variations resulted maximum sugar production of 14.9, 25.6% and HCN content of 21.9 & 13.1 mg/100g during different year time (2010 and 2009 when compared with 2008, respectively) probably due to variation in seasonal rainfall. Three years field study indicate that JS-2002 produced less HCN with low dose of N application (0 kg ha-1 ) and higher application of sulphur (40 kg ha-1 ) while more brix value at 40 kg S and 120 kg N ha-1 under sub-tropical rainfed conditions.