Fumonisin B1 is a mycotoxin that causes lethal pulmonary edema in swine. Sphinganine, sphingosine, and the sphinganine to sphingosine ratio are important biomarkers for fumonisin B1 exposure. Currently, tissues selected for sphinganine and sphingosine analyses are frozen at -80 degrees C until analyses take place. However, for diagnostics and some research projects, formalin is used more routinely as a preservative for long-term storage of tissues. To determine whether formalin-fixed tissues could be used for sphinganine and sphingosine analyses, sphinganine and sphingosine concentrations were quantified in both frozen and formalin-fixed lung, liver, kidney, and heart from fumonisin B1-treated and control pigs. Tissues were evaluated 3 months after freezing and 3, 6, and 12 months after formalin fixation. Sphinganine, sphingosine, and the sphinganine to sphingosine ratio of both frozen and formalin-fixed lung and liver from fumonisin B1-treated pigs were elevated. Formalin-fixed tissues had lower sphinganine and sphingosine concentrations but higher sphinganine to sphingosine ratios than the corresponding frozen tissues. Storage in formalin for up to 12 months did not affect the results. Sphingosine analysis could not be performed in formalin-fixed heart and kidney because of noninterpretable chromatograms. Therefore, formalin-fixed lung and liver can be used to determine fumonisin B1-induced sphinganine and sphingosine alterations in swine, with the sphinganine to sphingosine ratio being the most useful.