In a large cooperative study of Ga-67 uptake in non-Hodgkin's malignant lymphoma, 76% of untreated patients showed positive uptake in one or more lesions. The percentage of known individual lesions seen on scan was significantly lower; thus, negative findings at any one site may have much less significance than positive findings. After treatment, the number of lesions seen decreases sharply, but the role of Ga-67 in evaluating response to therapy is uncertain, especially in view of the fairly large number of lesions undetectable before therapy. Histologic type plays a role in Ga-67 uptake. Large lesions are much more effectively detected than small ones. In spite of numerous false-negative results, Ga-67 scanning is a useful method in evaluating the extent of untreated disease and the presence of lesions posttherapy.