Maize mitochondrial polyribosomes were isolated and characterized in the first and so far most complete study of the polysomal component of the translational apparatus of higher plant mitochondrial. Higher plant mitochondria are unique in that more than one, and often many, transcripts for a mitochondrial particular gene are found in abunDance; This made the characterization of the mRNA content of maize mitochondrial polyribosomes crucial to the understanding of information storage and use in these organelles;The protein gene transcript content of mitochondrial polysomes was described and compared to whole mitochondrial transcript content for seven maize mitochondrial genes. It was found that some selection among the multiple transcripts of several maize mitochondrial protein genes occurs at the polysomal level. For instance, the abundant 4.0 transcript of the atp6 gene was entirely missing from multimeric mitochondrial polysomal RNA. Most striking, however, was the observation that the majority of abundant transcripts of individual mitochondrial genes are bound to polysomes. This observation, coupled with recent reports that all plant mitochondrial polysomal transcripts sequenced to date are fully edited at the RNA level, suggests at least two hypotheses concerning gene expression in higher plant mitochondria: (1) there existed in the progenitors of these organelles a permissive transcription apparatus, and the (now nuclear) genome of the host evolved editing machinery to regulate the availability of the promiscuous transcripts to the mitochondrial translational apparatus; and/or (2) RNA editing and association with polysomes in plant mitochondria are developmentally and/or environmentally regulated in order to allow differential expression of the genome under different circumstances. Because only one developmental stage (dark-grown shoots) was studied in this work, this latter hypothesis remains an intriguing possibility;In addition, the translational regulation of a commercially important maize mitochondrial gene involved in cytoplasmic male sterility, T-urf13, was investigated in a revertant line. Cytoplasmic male sterility in race T maize (CMS-T) has been demonstrated to be strongly correlated with the levels of T-URF13 in CMS-T mitochondria. The levels of T-URF13 in TRf (revertant) maize are 25 to 40% of those in CMS-T mitochondria. Regardless of this, equal amounts of T-urf13 translatable in wheat germ extracts exist in both cytoplasms. In addition, work described in this dissertation indicates that preferential degradation of T-URF13 does not occur in TRf mitochondria. It was found that multimeric polysomes in CMS-T and -TRf mitochondria contain similar levels of T-urf13 transcripts, although there seems to be some enrichment of these transcripts in higher-order polysomes in CMS-TRf versus -T. T-URF13 levels associated with multimeric polysomes in the mitochondria of the two cytoplasms are lower (about 40% less) in CMS-TRf than -T. Apparently, similar levels of polysomally-bound transcripts do not necessarily yield similar, steady-state levels of polypeptide, at least in the case of T-urf13.