The technique of matrix assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (MS) allows for the mass determination of single oligomeric species that suffer from fragmentation effects using conventional MS techniques. Using MALDI, the sample to be analyzed is combined with a strong ultraviolet (UV) absorbing ''matrix,'' such as 3-hydroxypicolinic acid or 2,5-dihydroxybenzoic acid. Short UV laser pulses desorb the matrix plus sample material from the topmost sample surface, while simultaneously gently ionizing the sample material. The ionized species are then ejected into a time-of-flight analyzer for mass determination. The gentle ionization process allows oligomers on surfaces that would normally suffer from fragmentation effects to be detected intact. In this article, we describe an ultrahigh-vacuum MALDI instrument that has been constructed from primarily off-the-shelf components at minimal cost. This instrument may be used to detect the presence of picomole concentrations of material with atomic weights from a few hundred to over 100 000.