Controlled atmosphere (CA) storage of horticulture crops involves the holding of such produce in refrigerated storage with a reduction of oxygen and an increase in carbon dioxide. The effect of controlled atmospheres on the keeping quality of Centennial, Jersey, Goldrush, Nemagold, Oklamar, and Porto Rico sweetpotato varieties was studied in the 1963-65 period. Evaluations were made of decay loss, weight and dry matter loss, soluble solids percent, carotene content, taste of raw and baked roots, keeping after storage, and the ability of roots to sprout. In 1963-64, ranges of carbon dioxide from 0 to 15 percent were used in combination with 2 to 16 percent oxygen. Sweetpotato roots stored under atmospheres having an oxygen level below 7 percent or a carbon dioxide level above 10 percent developed a high percent of roots with either an alcoholic flavor or an off-flavor. Sweetpotatoes under an atmosphere of 3 percent carbon dioxide and 7 percent oxygen (3-7) had better quality than check lots as evaluated by low total losses due to decay and weight loss, higher dry matter content and a low dry matter loss, high total soluble solids and a high percent of acceptable tasting roots. The only disadvantage of this CA treatment was a higher loss due to decay upon holding at room temperature for one month after storage. However, this high loss was not significantly different from the open air check. In 1964-65 controlled atmosphere levels of 2 to 7 percent carbon dioxide in combination with 7 to 11 percent oxygen were used. Results similar to those of 1963-64 were obtained in 1964-65. Sweetpotatoes under an atmosphere of 2-7 in a gas generated CA room, had better storage quality as measured by low total losses, low dry matter disappearance, higher total soluble solids and a high percent of acceptable tasting roots compared to the checks. Roots removed from CA in 1964-65 and held at room temperature for one month did not exhibit the high decay found in the 1963-64 season. Decay was slightly higher than the check but not significantly different. The 2-7 atmosphere did not impair sprouting when roots were held at a warm temperature after storage. Sweetpotato roots under a 3-8 atmosphere in a sealed 55 gallon drum were relatively similar to roots held in the 2-7 room atmosphere, but were generally poorer in keeping quality. Sweetpotatoes under atmospheres 7-8 and 3-11 had lower total losses compared to the room air or open check, but not the covered drum check. Roots under these controlled atmospheres were not different from the covered check in dry matter loss and were higher in soluble solids, carotene content and percent acceptable tasting roots than the open check. Roots removed from the 7-8 and 3-11 atmospheres had higher decay losses than the checks after holding at room temperature for one month. The 7-8 and 3-11 atmospheres significantly decreased the ability of roots to sprout at room temperature. There were pronounced varietal responses to controlled atmosphere storage. CA holding had a beneficial effect on the Centennial and Jersey varieties and to a lesser degree on the Porto Rico and Goldrush varieties as evaluated by reduction of total losses, dry matter loss, higher soluble solids levels and a higher percent of acceptable tasting roots. More off-flavor developed in roots of the Nemagold and Oklamar varieties. The Nemagold and to a lesser degree the Oklawar had a higher total loss, dry matter loss, and lower soluble solids than the other varieties and after removal from CA and holding at room temperature the Nemagold variety developed more decay. / Ph. D.