Forty-four adult autologous transplant patients with hematological malignancies were randomized to receive either prophylactic parenteral nutrition PN (P group), or PN given ad hoc (C group). In each group, they were further randomized to receive standard PN (B group), or PN with 0.5 g glutamine/kg as L-Ala-L-Gln (A group). The overall survival (OS), disease-free survival (DFS) and event-free survival (EFS) in groups C vs. P and A vs. B were compared during follow-up with median 38 months. The final outcome rates in C/P/A/B groups, respectively (OS 65/81/63/85%, EFS 45/53/33/65% and DFS 56/50/35/77%), were not significantly different, apart from A < B in DFS rate (p=0.03, Fisher's exact test). Also in survival analysis (logrank test), no significant difference between groups C and P was found but generally worse parameters were observed for A vs. B group: for DFS (p=0.04) and EFS (p=0.01) the difference was significant, and for OS (p=0.09) it was borderline. In the three years' follow-up, no clinically useful benefit of prophylactic PN in autologous transplant patients was proven. Also, glutamine supplementation was not helpful, and was even connected with apparently worse long-term outcome.