Peptides can have widely varying solubility properties, depending largely on their primary sequence. While many peptides dissolve easily in bacteriostatic water, some, especially those containing multiple hydrophobic amino acid residues, may not readily dissolve. As a general procedure, we recommend first attempting to reconstitute peptides bacteriostatic water. If solubility is still a problem, addition of a small amount of dilute (approximately 10%) aqueous acetic acid (for basic peptides) or aqueous ammonia (for acidic peptides) may facilitate dissolution of the peptide. In most cases it takes these products 24-48 hours to completely dissolve in water.