Radon and its daughter decay products are thought to be the cause of 5% of lung cancer in the UK. This assessment has been made by the National Radiological Protection Board (NRPB) after a national survey of radon levels in homes, when more houses than anticipated were found to have high levels, and after a reappraisal upwards of the effectiveness of radon and its daughter products in causing lung cancer. A review of the scientific evidence reveals no direct evidence to incriminate radon or its decay products at the levels found in our homes in lung cell carcinogenesis. The issue involves different scientific disciplines and is highly complex. Debate between scientists is required and more epidemiological studies of lung cancer and low radon exposure are necessary. Meanwhile the indirect evidence linking low levels of radon exposure to lung cancer is insufficient to warrant the remedial action proposed by the NRPB and accepted by the UK government.

Many surgeons, particularly in the UK, give inadequate primary treatment to patients with operable breast cancer. For spurious reasons they regard axillary clearance as unnecessarily extensive surgery and rely instead upon total mastectomy or tumour excision and node sampling, with or without postoperative radiotherapy. But it is now clear that relapse-free and overall survival can be improved by appropriate adjuvant therapy. Thus inadequate exploration of the axilla is doubly unjustified. Not only is there the obvious risk of failure to remove nodes that contain metastases--so that some patients are deprived of cure by primary treatment--but the extent of tumour spread will be inadequately assessed in many more patients, with the risk that they may not receive appropriate adjuvant treatment.

The limitations of the kappa statistic method to measure inter-observer variation of categorical assessments are shown by means of a hypothetical example. Another method for assessing the inter-observer variation of categorical variables, the proportion of agreement, is used for the same example, and reasons why it is preferable to the kappa statistic are given. Since this method allows measurement of the inherent difficulty of carrying out a particular assessment, it has wide applicability in the introduction of new technology. If a proportion of agreement study shows poor inter-observer agreement for a new method, the technology must either be improved or abandoned.

Environmental stimuli responsible for inducing cutaneous inflammation include contact allergens and ultraviolet light. We postulate that these diverse stimuli trigger a cutaneous inflammatory response by directly inducing epidermal keratinocytes to elaborate specific pro-inflammatory cytokines and adhesion molecules. The consequences are activation of dermal microvascular endothelial cells and selective accumulation of specific mononuclear cells in the dermis and epidermis. Thus, keratinocytes may act as "signal transducers", capable of converting exogenous stimuli into the production of cytokines, adhesion molecules, and chemotactic factors (acting in an autocrine and paracrine fashion) responsible for initiation of "antigen-independent" cutaneous inflammation. The initiation phase may facilitate or promote an amplification phase with additional production of tumour-necrosis factor alpha and interferon gamma via an "antigen-dependent" pathway, and keratinocyte/T cell/antigen-presenting dendritic cellular associations. The direct activation of keratinocytes, with their ability to produce the complete repertoire of pro-inflammatory cytokines, can profoundly influence endogenous and recruited immunocompetent cells, thereby providing the critical trigger responsible for the swift and clinically dramatic alterations that occur following contact between the epidermis and a host of "noxious" agents.

The novel macrolide immunosuppressant FK 506 is a powerful and selective anti-T-cell agent which has a similar mode of action to that of cyclosporin. Clinical studies of FK 506 in liver allograft recipients indicate a lower risk/benefit ratio than with cyclosporin, and wider evaluation of FK 506 in transplant recipients is now under way in multicentre, prospective, controlled trials in both Europe and North America.

Cerebral malaria is a rapidly progressive encephalopathy with up to 50% mortality. A cardinal feature is the massing of red cells containing mature Plasmodium falciparum within the cerebral capillaries. Adhesion of these parasitised red cells to endothelium, an event which may initiate cerebral malaria, is being studied at the molecular level. However, the relevance of these studies to the pathophysiology and treatment of human cerebral malaria is uncertain. Although chloroquine is still widely used to treat falciparum malaria, resistance has spread to most of the endemic zone. Quinine is emerging as the only effective treatment for cerebral malaria, though resistance to this drug threatens to become a problem. Alternative drugs are urgently needed.