Abstract The use of coiled tubing (CT) is increasing rapidly in the oilfield service industry. Large CT sizes are being developed to meet new service requirements. The CT is being pushed closer to its performance limits for many of these services. To avoid CT failures in the field, it is important that these limits are well understood. There are three major types of CT limits: Life limits due to low cycle fatigue and corrosion of the CT.Pressure and tension limits of the CT [1].Diameter and ovality limits. These limits are interrelated in some ways but can be analyzed separately. The corrosion effect on the CT must be considered for the first two limits; but, the fatigue life of the CT does not significantly affect the pressure and tension limits.