Factors affecting progenitor cell mobilisation in patients with non-Hodgkin's lymphoma (NHL) are incompletely understood. We have analysed factors predicting mobilisation failure in 97 consecutive patients with NHL (59 males, 38 females; median age 49 years) who received mobilisation with intermediate-dose CY (4 g/m(2)) followed by G-CSF. The histology included large cell B (N=50), mantle cell (N=16), follicular (N=16) and other NHL (N=15). The disease status was 1CR/PR/primary refractory in 66 patients and >1 CR/PR in 31 patients. The minimum criterion for successful mobilisation was the collection of >or=1.5 x 10(6)/kg CD34(+) cells. In all, 18 patients (19%) failed to reach this threshold. In univariate analysis, premobilisation factors associated with mobilisation failure included BM involvement at the time of diagnosis (P=0.001) or prior to mobilisation (P=0.001) and low platelet count just prior to mobilisation (P=0.001). In multivariate analysis, only BM involvement at diagnosis (P=0.004) and platelet count just prior to mobilisation (P=0.01) were associated with mobilisation failure. A mathematical model based on these two factors and presented in the form of a receiver operating characteristics curve showed a sensitivity of 0.71 and a specificity of 0.77 in the prediction of mobilisation failure. Patients at a high risk of mobilisation failure may benefit from novel approaches.