Gradient-echo (GE) imaging with repetition times equivalent to those of T1-weighted spin-echo (SE) sequences and echo times for antiphase (opposed) transverse magnetisation have proved to be sensitive for high contrast imaging of focal lesions of red bone marrow. The sensitivity of antiphase GE sequences is due to the chemical shift between water-bound and fat-bound protons which introduces a tissue parameter that is not accessible by SE sequences. Main advantage of these GE sequences is the low signal intensity of intact red marrow and the high signal intensity of tumours and inflammatory lesions which allows, similar to T2-weighted SE sequences, for positive contrast imaging of lesions. In order to evaluate and to optimise the contrast-to-noise ratio (CNR) for red bone marrow and tumour 200 GE and 40 SE sequences with repetition times (TR) between 100 and 900 ms, echo times (TE) between 14 and 21 ms and flip angles (alpha) between 10 and 90 degrees were studied. CNR was measured and optimized regarding TR, TE, and alpha. The results indicate that opposed GE sequences, relatively independent from TR and alpha, are characterized by a high contrast-to-noise ratio. According to their high sensitivity for lesion detection they are suited to replace T2-weighted SE sequences.