Lipid microtubules are a promising vehicle for drug delivery to respiratory tract tissues. Targeted delivery requires an understanding of tubule aerodynamic behavior, for which predictive relations are available but have not been experimentally validated. This work compares predicted and observed tubule sedimentation behavior in a sheared flow environment such as that experienced in conducting airways. Lipid microtubules formed From 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3- phosphocholine (DC8,9PC) were nebulized from water suspension for 60 min and recaptured in a Stober spiral duct aerosol centrifuge. Samples were analyzed by light microscopy and atomic force microscopy. Tubules were straight with uniform diameter similar to 0.6 mu m, and remained straight during aerosolization and recapture. Observed aerodynamic behavior, as aerodynamic equivalent diameter, was compared with behavior predicted by fiber aerosol equations gleaned from the literature. Best agreement was obtained when tubule aerosol was modeled as partially hydrated thin-walled cylinders. These results were consistent with previous results for DC8-9PC aerosol and with expectations for evaporative core water loss from tubule ends.