The CIMT group achieved significant improvements in hand/arm movement that lasted up to a year following treatment, with the CIMT group having a faster performance time of 19.3 seconds to 9.3 seconds [52% reduction] over the control group's time of 24.0 seconds to 17.7 seconds [26% reduction] on the WMFT. Also the CIMT group achieved an increase from 1.21 to 2.13 vs from 1.15 to 1.65 in the control group in the MAL Amount of Use, and increase from 1.26 to 2.23 vs 1.18 to 1.66 on the MAL Quality of Movement scale. 2 year follow-up results: The effects at 24 months after treatment did not decline from those at 12 months for time taken to complete the WMFT (-0.32 s, 95% CI -3.70 to 3.06), for weight lifted in the WMFT (-1.39 kg, -2.74 to -0.04), for WMFT grip strength (-4.39 kg, -6.91 to -1.86), for amount of use in the MAL (-0.17, -0.38 to 0.04), or for how well the limb was used in the MAL (-0.14, -0.34 to 0.06). The additional changes were in the direction of increased therapeutic effect. For the strength components of the WMFT, p<0.0001. INTERPRETATION: Patients who have mild to moderate impairments 3-9 months poststroke have substantial improvement in functional use of the paretic upper limb and quality of life 2 years after a 2-week CIMT intervention. Thus, this intervention has persistent benefits.