This study was undertaken to calculate the incidence of 8 signs and symptoms used for the diagnosis of phlebitis with peripheral intravenous catheters, or short peripheral catheters, and the level of correlation between them. A total of 22 789 daily observations of 6 signs (swelling, erythema, leakage, palpable venous cord, purulent discharge, and warmth) and 2 symptoms (pain and tenderness) were analyzed of 5907 catheter insertion sites. Most signs and symptoms of phlebitis occurred only occasionally or rarely; the incidence of tenderness was highest (5.7%). Correlations were mostly low; warmth correlated strongly with tenderness, swelling, and erythema.