We developed, in bench-scale experiments, a unified loop-mediated isothermal amplification (LAMP) assay for the detection of cutaneous, mucocutaneous and visceral leishmaniasis using DNA of cultivated promastigotes. Two primer sets for the LAMP assay were designed based on the 18S rRNA gene, and their sensitivity and specificity were tested and compared. Both of them were specific for Leishmania as the DNA of all ten Leishmania species tested was amplified, whereas the DNA of other parasites, including that of Trypanosoma, was not. The detection limit for primer set 1 ranged between 30 pg and 3·6 fg, depending on which Leishmania species tested. Primer set 2 showed high sensitivity, but was less sensitive than primer set 1. Our findings lead to the conclusion that the LAMP assay with primer set 1 is a promising and effective assay for the successful detection of a wide range of Leishmania infections using only a unified multiplex LAMP test.