Lpx1p (systematic name: Yor084wp) is a peroxisomal protein from Saccharomyces cerevisiae with a peroxisomal targeting signal type 1 (PTS1) and a lipase motif. Using mass spectrometry, we have identified Lpx1p as present in peroxisomes, and show that Lpx1p import is dependent on the PTS1 receptor Pex5p. We provide evidence that Lpx1p is piggyback-transported into peroxisomes. We have expressed the Lpx1p protein in Escherichia coli, and show that the enzyme exerts acyl hydrolase and phospholipase A activity in vitro. However, the protein is not required for wild-type-like steady-state function of peroxisomes, which might be indicative of a metabolic rather than a biogenetic role. Interestingly, peroxisomes in deletion mutants of LPX1 have an aberrant morphology characterized by intraperoxisomal vesicles or invaginations.