The 2007 edition of the Thomson Reuters Journal Citation Reports, due to be released this week, will include the first official Impact Factors for no fewer than 12 BioMed Central journals as well as updated Impact Factors for 28 more.

As BioMed Central has previously noted, delays in "tracking” journals by Thomson Reuters mean that Impact Factors are often not made available as soon as they could be. Even when several years of citation data exists in the Web of Science "cited reference" database, the timing of publication of an Impact Factor in the Journal Citation Reports depends on when the journal was selected for tracking.

The availability of an alternative set of journal citation metrics, the SCImago journal rankings, based on Scopus data, has again called attention to this problem.

For example 3 of the 4 most highly cited journals at the top of SCImago’s Nutrition and Dietetics category are open access journals from BioMed Central (International Journal of Behavioral Nutrition and Physical Activity, Nutrition & Metabolism and Nutrition Journal). However, due to the timing of the tracking decisions made by Thomson Reuters, these journals will not receive official Impact Factors until June 2009, 2010 and 2011 respectively.

The good news is that the Thomson Reuters citation data does make it possible to calculate unofficial Impact Factors for BioMed Central journals – even those that are not yet listed in the JCR. The relatively straightforward to make this calculation, using the same formula used for the official Impact Factor calculation . We have now calculated the 2007 unofficial Impact Factors for around 100 BioMed Central journals, and this information are listed on our Impact Factor FAQ page.

 Some of the journals which have new or improved unofficial Impact Factors include:

Immunome Research	5.33
Particle and Fibre Toxicology	5.11
Implementation Science	4.43
Molecular Neurodegeneration	4.00
Cough	3.57
Frontiers in Zoology	3.24
Journal of Inflammation	3.19
Saline Systems	3.09
Immunity and Ageing	3.04
Proteome Science	2.63
Annals of Clinical Microbiology and Antimicrobials	2.42
BMC Geriatrics	2.42
BMC Clinical Pharmacology	2.38
Cell Division	2.37
BMC Biochemistry	2.34
Comparative Hepatology	2.20
BMC Physiology	2.12
Plant Methods	2.06
Health and Quality of Life Outcomes	2.00
BMC Medical Research Methodology	1.99
AIDS Research and Therapy	1.97
BMC Gastroenterology	1.90
Lipids in Health and Disease	1.88
BMC Pulmonary Medicine	1.85
Health Research Policy and Systems	1.79
BMC Complementary and Alternative Medicine	1.61
Journal of Neuroengineering and Rehabilitation	1.60
Scoliosis	1.59
BioMedical Engineering Online	1.58
Nutrition Journal	1.56
Clinical and Molecular Allergy	1.55
BMC Medical Informatics and Decision Making	1.53
Human Resources for Health	1.43
Clinical Practice and Epidemiology in Mental Health	1.43
BMC Medical Ethics	1.40
International Journal for Equity in Health	1.40
Harm Reduction Journal	1.34
BMC Veterinary Research	1.33
Nutrition and Metabolism	1.32
Journal of Ethnobiology and Ethnomedicine	1.23
BMC Family Practice	1.07
Globalization and Health	1.04
Cardiovascular Ultrasound	1.04

As for the new official Impact Factors – watch this space!