A panoramic sight of epidemiological, clinical and experimental studies, referring to Loxosceles laeta and loxoscelism, carried out in 1955-1988, in Santiago, Chile is presented. Two-hundred and sixteen cases of loxoscelism were studied. The most relevant features were: 84.3% corresponded to cutaneous loxoscelism (CL) and 15.7% to viscerocutaneous loxoscelism (VCL); 73.6% occurred in hot season; in 86.6% of cases the accident happened in the house, particularly in bedrooms, while the people were sleeping or dressing. The spider was seen in 60.2% of cases and identified in the laboratory as L. laeta in 10.6% of all cases. The sites more frequently bitten were the limbs with 67.6%; a burning-stinging was the most frequent initial symptom. Pain, edema and livedoid plaque, which developed later into a necrotic eschar, were the predominant local manifestations. In VCL, hematuria and hemoglobinuria were constant, while jaundice, fever and sensorial involvement were present in most of the cases. CL patients were parenterally treated with antihistaminic drugs or corticoids, while VCL ones were treated with corticoids by injection. The condition of patients in the last follow up was: complete cure in 75.5%, cure with a scarfed sequela in 8.3%, death in 3.7% (all VCL) and abandonment in 12.5%. Additionally, a series of experimental studies, both in vivo and in vitro, has been performed in order to clarify basic aspects on L. laeta venom and the treatment of loxoscelism.