The authors present a biomicroscopic evaluation of vitreal alterations in a large group of patients affected by primary retinitis pigmentosa (RP). 286 RP patients (571 eyes), 153 (305 eyes) males and 133 (266 eyes) females, have been studied; the mean age of this whole group was 37.26 + or - 14.93 years (age range: 5-77). Vitreal static and dynamic biomicroscopy was performed on fully dilated pupils by means of a Haag-Streit 900 slit-lamp and high-power positive precorneal lenses (+90 and +78 dpt Volk lenses). Most patients showed floating cottonball-like condensations (26.824%) often associated with fibrillary degeneration (15.88%), while non-pigmentary vitreal particulation was detected in 26.609% of cases and the pigmentary type in 12.017%, respectively. Posterior vitreal detachment was detected alone in only 0.43% of cases while 18.24% of examined eyes showed no vitreal alterations. A high statistical correlation between vitreal aspects and pigmentary grading of the fundus oculi (p = 0.0001), as well as duration of the disease (p = 0.0074), was found; at the same time, no statistical correlation with refractive error was demonstrated (p = 0.47).