Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant disease that usually manifests itself within the fifth decade. The most prominent symptoms are progressive ptosis, dysphagia, and proximal limb muscle weakness. The disorder is caused by trinucleotide (GCG) expansions in the N-terminal part of the poly(A)-binding protein 1 (N-PABPN1) that result in the extension of a 10-alanine segment by up to seven more alanines. In patients, biopsy material displays intranuclear inclusions consisting primarily of PABPN1. Poly l-alanine-dependent fibril formation was studied using the recombinant N-terminal domain of PABPN1. In the case of the protein fragment with the expanded poly l-alanine sequence [N-(+7)Ala], fibril formation could be induced by low amounts of fragmented fibrils serving as seeds. Besides homologous seeds, seeds derived from fibrils of the wild-type fragment (N-WT) also accelerated fibril formation of N-(+7)Ala in a concentration-dependent manner. Using atomic force microscopy, differences in fibril morphology between N-WT and N-(+7)Ala were detected. Furthermore, fibrils of N-WT showed a lower resistance against solubilization with the chaotropic agent guanidinium thiocyanate than those from N-(+7)Ala. A systematic modulation of fibril formation kinetics was studied with proteins like RCMLA, Lysozyme and a deletion mutante of N-PABPN1. A poly-alanine peptide enhanced fibril formation rates. Experiments with inorganic salts showed an strong acceleration of fibrillation rates by sulfate anions because of salting out effects. The addition of L-arginine results in a delay of the fibrillation rates and in a reduction of the amount of fibrils. Doxycycline and trehalose, compounds that have been found to mitigate OPMD symptoms in animal models, surprisingly accelerated fibril formation.