In the 5`UTR of transcripts of the Chlamydomonas chloroplast gene rbcL secondary structures in the shape of two stem loops, one large and one small, have been identified. The large stem loop has been found to mediate folding of a ten nucleotides long sequence, stretching from position +38 to +47 relative to the transcription start site (TSS) (+1). This region has been found crucial for transcript stability. If its sequence, and/or partially its conformation, is disturbed, transcripts will be rendered unstable. Little focus has been aimed at the smaller loops function. In this study a deletion of nucleotides between positions +54 and +95 in the 5´ UTR of rbcL still renders stable transcripts, suggesting that the deleted region is not essential for transcript stability. This helps to narrow down the sequence and the number of nucleotides where a cis-acting element could be located, and to identify trans-acting factors believed to bind to this element, aiding in stabilizing the transcripts of the C. reinhardtii chloroplast gene rbcL.