This study focused on several factors that may influence the percentage of motile microorganisms in a sample from the tongue determined using a phase-contrast microscope. It was found that the time elapsing between sampling and analysis is crucially important. In both sterile saline and reduced transport fluid (RTF), a reduction of the percentage of motile microorganisms was found within 15-30 min after sampling respectively. In order to be able to prolong the time interval between sampling and analysis, it was found that storing a sample in a tuberculin syringe with RTF supplemented with Fildes extract preserved the motility of the microorganisms and gave no significant reduction in the percentage of motiles within 48 h.