This study encompasses a collection of experiences with regard to numerous matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) sample preparation techniques in terms of their suitability for different peptide and protein analytes. Variants of both established and new sample preparation techniques for the MALDI-MS analysis of peptides and proteins are described. The importance of matrix selection, matrix and analyte concentration, pH adjustment, crystallization conditions and the use of additives is evaluated. The tolerance of the different sample preparations towards salts, buffers, synthetic polymers, detergents, denaturants and other contaminants, and also the influence of the preparation methods on undesired amino acid side-chain oxidation, are investigated. Moreover, the performance of on-target tryptic digestion and on-target disulfide reduction is shown and a microscale purification procedure is described. According to this study, there is no universally applicable sample preparation for a broad variety of analytes. Rather, it is necessary to specifically adapt the sample preparation to the analyte properties. © 1997 John Wiley & Sons, Ltd.