We have constructed artificial linear mini-chromosomes for the parasitic protozoan Trypanosoma brucei. These chromosomes exist at similar to 2 copies per cell, are indefinitely stable under selection but are lost from 50% of the transformed population in ~7 generations when grown in the absence of selective pressure, Consistent with results obtained earlier with natural chromosomes in T.brucei, the telomeres on these artificial chromosomes grow, adding ~ 1-1.5 telomeric repeats per generation, The activity of a procyclic acidic repetitive protein (parp) gene promoter on these elements is unaffected by its proximity to a telomere, implying the lack of a telomere-proximal position effect (TPE) in procyclic trypanosomes, Among other things, these autonomously replicating dispensable genetic elements will provide a defined system for the study of nuclear DNA replication, karyotypic plasticity and other aspects of chromosomal behavior in this ancient eukaryotic lineage.