Lymphatic metastasis has always been regarded as a major prognostic indicator for disease progression and as a guide for therapeutic strategies to oral squamous cell carcinoma (OSCC), but to date, how tumor cells access and spread via the lymphatics have not been fully elucidated. Whether tumor cells metastasize by expansion and invasion of pre-existing peritumoral lymphatics or by the induction and invasion of newly formed lymphatics within tumors is controversial. In order to address this issue and find out the clinicopathological significance of intratumoral lymphangiogenesis, we investigated 86 archival specimens from patients with OSCC, quantitating lymph vessels by immunostaining with D2-40. We also quantified lymphatic invasion and examined the possible associations of all the above parameters with clinicopathological features and outcome. Higher intratumoral lymphatic density (ILD) and peritumoral lymphatic density (PLD) were both significantly associated with the presence of lymph node metastasis at the time of diagnosis and the outcome of the post-operation biopsy of 77 patients (P = 0.001). Higher ILD was significantly associated with a higher incidence of intratumoral lymphatic invasion, peritumoral lymphatic invasion and recurrence of tumor (P = 0.001 and P = 0.041 and P = 0.001, respectively). Patients with higher ILD exhibited shorter 5-year cumulative and disease-free survival (P = 0.001). Thus, lymphangiogenesis indeed occurs in oral squamous cell carcinoma; ILD might be used as an index to inflect the aggression of the disease, to evaluate the status of lymphatic metastasis, to separate patients at higher risk of an adverse clinical outcome.