Participations in participation bonds held by a scheme manager are not 'trading stock' within the meaning of section 1 of the Income Tax Act 58 of 1962. Such participations constitute secured interest-bearing loans by participants to mortgagors, not items held for purposes of sale or exchange. When a manager replaces its own participation with a new participant, this does not constitute a sale, exchange, cession or disposal - rather, the mortgagor's debt to the manager is discharged and a new debt is created to the incoming participant. For something to be trading stock under the first part of the definition, it must be acquired for purposes of sale or exchange, which requires an identifiable merx and pretium. For the second part of the definition to apply, there must be a disposal with identifiable proceeds forming part of gross income. Neither requirement is satisfied by participation bond investments held by scheme managers.