Purpose: To assess the influence of different topical steroid agents and a non-corticosteroid medication after Argon laser trabeculoplasty (ALT) on the development of peripheral anterior synechiae (PAS) and the reduction of intraocular pressure (IOP). Method: In two separate prospective, randomised, group-controlled studies, topical fluorometholone 0.1% (FML Liquifilm) was compared with dexamethasone 0.1% (Maxidex) (Study A), or naphazoline hydrochloride 0.1% (Albalon) (Study B) after ALT for chronic open-angle glaucoma, with particular reference to the formation of PAS and the IOP response. Results: In Study A (N = 109) eyes treated with Maxidex had a significantly higher incidence of PAS than those treated with FML - 45% compared with 22%, P < 0.05 (normal deviate test). In Study B (N = 75) the incidence of PAS was equal in eyes treated with FML or Albalon (23%). In the two studies combined (N = 184), the development of PAS was associated with a significantly lower mean response of IOP to ALT - 1.47 mmHg compared with 3.22 mmHg, 0.01 < P < 0.05 (Student t-test). CONCLUSION: The incidence of PAS after ALT is significantly higher with the post-laser use of Maxidex than with FML, and is the same for Albalon as for FML. The therapeutic benefit of ALT is significantly reduced if PAS develop.