The present invention provides peptides consisting of L- and/or D-amino acids and combinations thereof, which affect platelets by action on the collagen receptor, glycoprotein VI (GPVI). More specifically, however, the peptides act on the GPVI-FcRγ signaling complex. The invention also provides lipid and sugar conjugated peptides comprising L- or D-amino acids. The invention still further provides a method of designing of the peptides and lipid- and/or sugar-conjugated peptides comprising L- or D-amino acids. The present invention further relates to the therapy of various disease states involving the use of these peptides and compounds. Specifically, the peptides and compounds are useful in the treatment and/or prevention of a disease or condition involving platelet activation and aggregation, and more particularly, collagen-induced platelet activation and aggregation. They also are useful in the production of medical devices comprising peptide matrices (i.e., for example, cardiovascular stents).