This study is the first report of the permeability status of nailfold capillaries in psoriatic arthritis (PA). "Traditional" nailfold capillary microscopy and intravital fluorescence videomicroscopy were carried out at the nailfold of 13 patients with PA. Twenty five healthy subjects served as controls for nailfold capillary microscopy, and 15 out of these for fluorescence videomicroscopy. The following parameters were assessed: capillary length, apex width, maximum loop width, maximum limb width, loop density, visibility of subpapillary venular plexus, loop tortuosity, transcapillary diffusion, and interstitial concentration at different sites and times of Na-fluorescein given in intravenous bolus. Morphometric analysis of capillaroscopic findings showed a significant increase of loop length (mean +/- SD: 290.1 +/- 73.5 microns) when compared to healthy controls (223.3 +/- 51.9 microns) (P < 0.02). Transcapillary passage of Na-fluorescein was homogeneous and symmetric both in PA patients and in controls. Mean transcapillary and interstitial diffusion was not significantly enhanced at the nailfold in PA patients. Our data support the view that PA is not characterized by a specific capillaroscopic pattern and/or significant abnormalities of microvascular dynamics at the nailfold.