Purpose: To monitor red blood cell (RBC) shape evolution by 1 H 2 O diffusion–diffraction NMR in time steps compara - ble to those required for the acquisition of a 31 P NMR spectrum; thus, to correlate RBC mean diameter with ATP concentration after poisoning with NaF. Materials and Methods: Pulsed-field gradient-stimulated echo (PFGSTE) diffusion experiments were recorded on 1 H 2 O in RBC suspensions. Under conditions of restricted diffusion, q -space experiments report on mean RBC diam- eter. To decrease experiment time, the phase cycling of radiofrequency (RF) pulses was cut to two transients by using unbalanced pairs of gradient pulses. Data processing used a recent digital filter. Differential interference contrast (DIC) light microscopy also recorded shape changes. 31 P NMR spectroscopy gave estimates of mean ATP concentra- tion. Results: NaF caused RBC-shape evolution from discocytes, through various forms of echinocytes, to spherocytes, over 6 h and 10 h at 37°C and 25°C, respectively. ATP de- clined to 0.5 its normal concentration before the first stage of discocyte transformation; the concentration was 0.0 after 1.5 h and 3.0 h, respectively, at the two temper- atures. Conclusion: RBC shape was readily monitored by NMR with a temporal resolution that was useful for correlations with both DIC microscopy and 31 P NMR spectra.