RT-PCR and Northern blot analysis were performed in order to search for a putative beta-adrenergic receptor (β-AR) in Paramecium using several β2-adrenergic-specific molecular probes.Under strictly defined RT-PCR conditions DNA species of expected molecular size about 360 bp were generated with the primers corresponding to the universal mammalian β2-AR sequence tagged sites (located within the 4th and the 6th transmembrane regions of the receptor). This RT-PCR product hybridized in Southern blot analysis with the oligonucleotide probe designed to the highly conservative β2-AR region involved in G-proteins interaction and located within the amplified region. Northern hybridization was performed on Paramecium total RNA and mRNA with human β2-AR cDNA and two oligonucleotide probes: the first included Phe 290 involved in agonist binding (Strader et al., 1995) and the second was the backward RT-PCR primer. All these probes revealed the presence of about 2 kb mRNA which is consistent with the size of β2-AR transcripts found in higher eukaryotes.