Abstract Tapioca constitutes one of the staple foods prepared in different forms for consumption by many African dwellers, including Nigeria. It is a processed food from Manihot esculenta (cassava), rich in carbohydrate and contains linamarin that produces the toxic compound, hydrogen cyanide (HCN). Samples were collected from six selected areas: Bua-Yeghe, Sogho, Ebubu, Igbodo, Baa-Goi and Eneka in Rivers State to determine the starch and cyanide contents of the unprocessed cassava and tapioca, using the picrate and spectrophotometric methods respectively. The results of detectable values (%) for starch were: 4.65±0.74, 6.30±0.70, 3.80±0.43, 2.63±0.34, 5.81±0.57 and 6.29±0.60, while cyanide concentrations (mg/Kg) were: 3.20±0.43, 7.54±0.50, 5.57±0.55, 1.76±0.36, 11.31±0.92 and 10.31±1.06 respectively. The unprocessed M. esculenta gave 18.56±2.64 and 27.78±4.26 for starch and cyanide respectively. There was significant variation (p<0.05) between the processed and the unprocessed forms, implicating sources other than linamarin as the only probable source of cyanide. The results obtained from the unprocessed cassava which showed that cyanide concentrations were higher than the 10 mg HCN per kilogram as recommended by FAO/WHO was expected, but those from tapioca fell below the threshold limit, except those from Baa-Goi and Eneka, which are slightly above the international standard, signifying possible exposure of consumers of the food to toxicity. The study also noted differences (%) in starch and cyanide contents of the unprocessed cassava and tapioca, which ranged from 64.25-94.24% for cyanide and 62.15-88.41% for starch at the various sample sites as the extraction of starch and cyanide contents continued each day, following soaking, for five days. The study concluded that the processing method employed could be considered effective in reducing cyanide in tapioca, but may grossly affect the taste of tapioca and the dietary requirement for carbohydrate for such a meal.