The lead concentration in CSF was determined by flameless atomic absorption spectrophotometry in 16 ALS patients and 22 control cases. The mean values were 0.69 +/- 0.55 (ALS) and 0.41 +/- 0.37 (controls), P < 0.01. This confirms our earlier findings of raised CSF lead levels in ALS but the present values are lower than previously reported for both ALS patients and controls.