Lowering the annealing temp and increasing the annealing time plus the addition of 5% DMSO helps my GC-rich PCR (Myxococcus). My primers usually have Tm's of about 85-90 degrees. I usually use 95 1', 50-55 2' and 72 1'/kb expected product. -- Don Walthers B.S.Microbiology U of Illinois at UC, 1996 Ph.D. Microbiology U of Idaho, 2001? gene_jockey26 at yahoo.com