Most canine patients treated for lymphoma (>80%) will achieve complete remission. Cures, however, are rare and pets relapse and die of their disease. The cause of this relapse is the presence of residual malignant cells that eventually grow and become clinically detectable. With the advent of more sensitive molecular techniques the measurement of minimal residual disease (MRD) could be incorporated into clinical case management to optimize treatment strategies; improve patient outcome, and to gain additional insight into the basic biology of lymphoma. To date serial blood samples from 68 canine patients with lymphoma undergoing treatment taken at a variety of time points have been collected. Concerning follow up of those patients, 56 have died of their lymphoma, 3 have died of other non-cancer causes. Nine patients are still alive as of 9/26/11. Of those 9, 4 had come out of remission and completed sample collection, 5 are still in remission but we have stopped sample collection in those patients. A total of 555 samples have been collected from these 68 patients with an average number of samples per patient of 8. Immunophenotype and treatment characteristics of these 68 patients are as follows; 50 are B cell, 16 are T cell, one has both markers, and one is pending. From a treatment standpoint, 37 dogs received a multiple drug chemotherapy protocol (35= CHOP, 2 COP), 26 received doxorubicin single agent therapy, and 5 received investigational drugs as part of a clinical trial. Extraction of DNA, development of patient specific primers, and analysis of quantitative MRD is ongoing. All patient information has been collected and complied at this point and will be correlated with molecular assay results when they become available. With this information we will answer the following questions: Does the level of molecular disease burden at the time of diagnosis and at the end of chemotherapy (i.e. the magnitude of decrease) correlate with remission length and overall survival. We hypothesize that it will.