Characterized by presence of erythrosquamous well defined, lesions with a predilection for extensor surface of the body often associated with nail and joint involvement, having a course of relapses and remissions. Aetiology and epidemiology-onset-any age, equal sex incidence, theories of aetiology, inheritance-genetic inheritance or mutation, provocative factors-trauma (koebner’s phenomena), infection (streptococcal sore throat), stress-psoriasis gets aggravated by stress, weather/climate (hot weather improves psoriasis), metabolic (hypercalcaemia, diabetes mellitus), drugs (chloroquine, beta-blockers, corticosteroid with drawl after prolonged). Histopathology: Parakeratosis, elongation of rete ridges, elongation and oedema of dermal papillae. Thinning of suprapapillary. Common types of presentation are as follows-Psoriasis vulgaris, guttata psoriasis, nummular psoriasis Flexural psoriasis, Palmoplantar psoriasis, Pustular psoriasis. Common feature: Well-defined, erythematous, scaly lesions, common sites-scalp, trunk and extensor surface of extremities, koebner’s phenomena-occurrence of isomorphic lesions at sites or trivial trauma, auspitz sing-presence of punctuate bleeding spots on removal of seales by a slide, Woronoff’s sign-presence of a whitish ring round the psoriatic plaques, Nails changes: Thimble pitting, oil drop appearance, Onycholysis, Onychodystrophy. Joints: Arthritis, Seronegative. Complications: Erythroderma, Infections, Arthritis, Eczematization, Amyloidosis. Treatment of psoriasis—no full proves curative treatments. Local treatment-Coal tar bath, local application of urea cream 20 percent, PUVA therapy, and UVA/narrow brand UVB phototherapy with psoralen group drug is useful, in resistant cases Tab methotrexate (2.5 mg) 1-2 tab 2-3 times a week with initial and periodic check up, local application of calcipotriol.