The authors (C.B.G., F.B.P., F.C., F.F., and N.P) checked the effectiveness of the iridotomy performed by picosecond Nd: YLF laser in the primary acute glaucoma. Fifteen eyes underwent the iridotomy laser during the 12 hours after the diagnosis. No local therapy was administered before or immediately after the treatment. Eight patients who were positive to the dark-room test one month after the treatment underwent the laser iridotomy in the controlateral eye. The authors observed a good ocular pressure control in more than 90% of the patients at the end of a four month follow up. The iridotomy made by picosecond Nd: YLF laser shows regular margins and poor perilesional damage. The total energy employed is higher than Nd: YAG laser; nevertheless, the low level of energy erogated for each pulse is less harmful for the tissue