A Study to Compare the Safety and Efficacy of Dysport® and Botox® in Adults With Upper Limb Spasticity.

Inclusion Criteria: * Participant must be 18 to 80 years of age inclusive, at the time of signing the informed consent * 2a. \[US/France\] Participants with stable Upper Limb Spasticity (ULS) for at least 3 months, in whom treatment of only one upper limb is necessary for the duration of the study; * 2b. \[Canada\] Participants with stable post-stroke ULS for at least 3 months, in whom treatment of only one upper limb is necessary for the duration of the study * Participants who are either naïve to Botulinum toxin type A (BoNT-A) for ULS or who have been previously treated with BoNT-A for ULS; * Participants with MAS score of at least 2 at two muscle groups (one of these two muscles groups should be the PTMG) and at least 1 in the remaining muscle group. * Participants with DAS score of at least 2 on the Principal Target of Treatment (PTT) (one of four functional domains: dressing, hygiene, limb position and pain); * Participants who require BoNT-A injection in all of the following muscles: flexor carpi radialis, flexor carpi ulnaris, flexor digitorum profundus, flexor digitorum superficialis and biceps brachii; * Participants for whom injection of a total dose of 900 Units aboBoNT-A or 360 Units onaBoNT-A is considered by the investigator to be clinically appropriate; * Participants who have been stable for at least 3 months prior to study entry in terms of oral antispasticity, anticoagulant and/or anticholinergic medication if treated are considered by the investigator likely to remain stable for the duration of the study; Exclusion Criteria: * Major limitations in the passive range of motion in the paretic upper limb; * Major neurological impairment (other than limb paresis) that could negatively affect functional performance; * Participants clinically requiring injection into any upper limb muscles other than the five muscles of one arm listed in Section 5.1, or requiring injection into both arms or any lower limb within the timeframe of the study; * Hypersensitivity to any BoNT product or excipients; * Hypersensitivity to cow's milk protein (casein); * Infection at the proposed injection site(s); * Known peripheral motor neuropathic diseases, amyotrophic lateral sclerosis or neuromuscular junction disorders (e.g. myasthenia gravis or Lambert-Eaton syndrome); * Any medical condition (including dysphagia or breathing difficulties/compromised respiratory function) that in the opinion of the investigator, might jeopardize the participant's safety; * Women who are pregnant or lactating * Participants treated with BoNT of any type for any indication (e.g. bladder injection, headache or cosmetic) within the previous 12 weeks or planned/likely to be treated during the course of the study; * Prior history of non-responsiveness to BoNT treatment; * Previous surgery, or administration of alcohol or phenol in the study limb 6 months or earlier from study enrolment or planned/likely to be treated during the course of the study; * Participants treated with intrathecal baclofen (except if treatment has reached a stable dose for \>4 weeks and is likely to remain stable throughout the study), aminoglycosides or other agents interfering with neuromuscular transmission (e.g. curare-like agents) within the 4 weeks prior to study enrolment or planned/likely to be treated during the course of the study * BoNT naïve participants with a history of facial neurogenic disorder (facial paralysis, polyradiculoneuropathy) (only for France). * Participants receiving concomitant medication treatment with the following PT/OT interventions on the study limb: new splinting/orthotics/casting, serial casting, shockwave therapy, dry needling and needle tenotomies. However, PT/OT interventions not intended to reduce study limb spasticity (e.g. functional training exercises) or with a transient (\<1 day) reduction of study limb spasticity (e.g. stretching, weight bearing) are allowed.