After an epidemic of giardiasis, some patients experienced persisting abdominal symptoms despite becoming Giardia-negative in stool samples after metronidazole treatment. The study aimed to determine if these patients were suffering from treatment refractory, chronic, cryptic giardiasis. The design was a prospective randomized open clinical trial with 1 arm receiving anti-Giardia treatment in the form of albendazole and metronidazole (A/M) for 7 d (n=12) and the other arm receiving tetracycline and folic acid (T/F) for 28 d (n=13). Symptom scores and global improvement were outcome measures. Symptom scores were analysed regarding time and treatment using mixed linear modelling. In both groups total symptom scores improved at the end of treatment; the improvement was significant for the T/F group. Bloating decreased significantly in both groups at the end of treatment. One month after treatment, 3 patients in the T/F group (23.1%) and 1 patient (8.3%) in the A/M group reported global symptom improvement. Symptoms recurred in all of these, and after 1 y total symptom scores were unchanged from baseline in either group. Treatment of post-giardiasis persistent abdominal symptoms with T/F or A/M resulted in only temporary symptom relief, possibly due to the anti-inflammatory effect of both treatments. Cryptic chronic giardiasis was not the explanation for the persistent symptoms.