Serum LDH levels have been found to be significantly increased in non- Hodgkin lymphoma (NHL) patients, both histiocytic and lymphocytic. The duration of survival of NHL negatively correlates with the level of serum lactic dehydrogenase (LDH), and statistical analysis reveals that patients with lower levels of LDH have a longer survival rate than the patients with higher LDH activity, irrespective of their histologic classification. The analysis of the results by the Test for Trend in Prognosis allows us to establish that the correlation of the rate of survival and LDH levels is independent from other clinical parameters.