To evaluate the efficacy of the nonsteroidal anti-inflammatory drug etodolac, a comparative, double-blind study versus piroxicam was carried out Two homogenous groups (in term of age, sex, time since last crisis and duration of present episode) of patients suffering from acute lumbar pain were treated during one week with either etodolaco, 300 mg b.i.d; (n = 30) or piroxicam 20 mg/day plus placebo (n = 31). Diagnosis was confirmed by history, physical examination, and Rx studies. Several clinical parameters were assessed prior and after treatment. All 61 patients completed the study. Adverse drug reactions were evaluated in the final visit. No significant differences were established between groups in relation to efficacy. Compared to baseline, statistically significant relief of symptoms was achieved in both groups, for pain intensity (p < 0.005); sleep quality (p < 0. 006), paravertebral muscles spasm (p < 0. 005) and spinal range of motion (p < 0.005). Patients treated with etodolac exhibited significantly less adverse reactions than those on piroxicam (p < 0.025).